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TN295 



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No. 9105 



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Bureau of Mines Information Circular/1986 



A Columbium-Bearing Regolith on 
Upper Idaho Gulch, Near Tofty, AK 

By J. Dean Warner, C. L. Mardock, and D. C. Dahlin 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9105 



A Col umbi urn-Bearing Regolith on 
Upper Idaho Gulch, Near Tofty, AK 

By J. Dean Warner, C. L. Mardock, and D. C. Dahlin 




UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Model, Secretary 

BUREAU OF MINES 
Robert C. Morton, Director 




no. ■jios 



Library of Congress Cataloging-in-Publication Data 



Warner, J. 


Dean 








A columbium-bearing regolith 


on upper Idaho Gulch 


near Tofty, AK. 


1 Information 


circular; 9105) 








Bibliographv 


;p.l9. 








Supt. of Docs 


. no.: I 28.27: 9105, 








1. Niobium ores — Alaska — Tofty Region. 2. Ore-deposits — Alaska — Tofty Region. 3. 
Geology— Alaska— Tofty Region. I. Mardock, C. L. (Cheryl L.) II. Dahlin, D.C. (David 
ClifTord), 1951- . III. Title. IV. Series: Information circular (United States. Bureau of 


Mines); 9105. 










TN295.U4 


(TN490.N65) 


622 s 


(553.4'99) 


86-600130 



PREFACE 



This is one of a series of Bureau of Mines reports that present the findings of 
reconnaissance-type mineral assessments of certain lands in Alaska. These reports 
include data developed by both industry and government studies. 

Assessing an area for its potential for buried mineral deposits is a difficult task 
because no two deposits are identical. Moreover, judgments prior to drilling, the 
ultimate test, frequently vary among evaluators and continue to change as a result of 
more detailed studies. 

Included in these reports are estimates of the relative favorability for discovering 
mineral deposits similar to those mined elsewhere. Favorability is estimated by 
evaluation of outcrops, and analyses of data, including mineralogy, geochemistry, and 
evaluation of rock-forming processes that have taken place. Related prospects and the 
environment in which they occur are subjectively compared to mineral deposits and 
environments in well-known mining districts. Recognition of a characteristic 
environment allows not only the delineation of a trend but also a rough estimate of the 
favorability of conditions in the trend for the formation of minable concentrations of 
mineral materials. 



CONTENTS 



111 



Page 

Preface i 

Abstract 1 

Introduction 2 

Acknowledgments 2 

Location and accessibility 2 

Physiography 3 

Land status 3 

Previous investigations 3 

Bedrock geology of the Tofty area 4 

Nature and extent of present investigations 5 

Geology of the regolith 5 

Mineralogy and petrography of the regolith 6 

Regolith sampling 8 

Methods and results 8 

Interpretation 11 

Magnetic, radiometric, and soil sample surveys on 

upper Idaho Gulch 12 

Methods and results 12 

Interpretation 12 



Page 

Columbium resources 16 

Beneficiation of columbium from the regolith .... 16 

Discussion 18 

Origin of the regolith 18 

Sources of placer minerals 18 

Summary and conclusions 19 

References 19 

Appendix A. — Modified 1956 drill core logs and 

geologic cross sections constructed from drill core 

data 20 

Appendix B.— Test procedure for characterization 

of Tofty regolith concentrates 5, 9, 15, and 30 . . . 24 
Appendix C. — Results of emission spectrographic 

analyses of regolith samples 25 

Appendix D. — Results of magnetic, radiometric, 

and soil sample surveys 26 



ILLUSTRATIONS 

Page 

1. Location of study area 2 

2. Aerial view of Idaho Gulch showing trenches 3 

3. Tofty tin belt, Alaska 4 

4. Locations of trenches and drill holes and mapped extent of the regolith 5 

5. Scanning electron microscope photomicrograph and columbium X-ray scan of columbium-rich portion of 

regolith concentrate 7 

6. Scanning electron microscope photomicrograph of broken aeschynite grain from regolith concentrate .... 7 

7. Locations of samples collected in trench T-5 8 

8. Locations of samples collected in trench T-8 8 

9. Locations of samples collected in trenches T-2, T-3, and T-4 9 

10. Locations of 1956 channel samples in trench T-8 11 

11. Residual magnetic intensities within surveyed area on upper Idaho Gulch 13 

12. Total-count gamma-ray radioactivity within surveyed area on upper Idaho Gulch 14 

13. Columbium, zinc, and P2O5 concentrations in soils within surveyed area on upper Idaho Gulch 15 

14. Flow diagram of columbium beneficiation procedure 16 

A-1. Geologic section through drill holes D-1 and D-2 and trench T-8 22 

A-2. Geologic section through drill holes D-3 and D-6 and trench T-8 22 

A-3. Geologic section through drill hole D-7 and trench T-8 22 

A-4. Geologic section through drill hole D-8 and trench T-8 23 

A-5. Geologic section through drill hole D-9 and trench T-8 23 

A-6. Geologic section through drill holes D-4 and D-5 and trench T-6 23 



TABLES 

1. Results of analyses of samples of pan-concentrated regolith 6 

2. Estimated ranges for mineral content in minus 20-mesh fraction of samples of pan-concentrated regolith 7 

3. Results of XRF analyses of regolith samples 9 

4. Results of analyses and descriptions of rock specimens 10 

5. Results of XRF analyses for columbium in channel samples collected from trench T-8 in 1956 10 

6. Results of 1956 emission spectrographic and chemical analyses for columbium in sludge samples of 

regolith 10 

7. Results of analyses of composite samples of marble from drill hole D-4 10 

8. Gravity and magnetic concentration of sample A 17 

9. Gravity and magnetic concentration of sample B 17 

10. Trace-element abundances and variations in reported carbonatite deposits and marble and regolith on 

upper Idaho Gulch 18 

A-1. Log of diamond drill hole D-1, Idaho Gulch 20 

A-2. Log of diamond drill hole D-2, Idaho Gulch 20 



IV 



A-3. Log of diamond drill hole D-3, Idaho Gulch 

A-4. Log of diamond drill hole D-4, Idaho Gulch 

A-5. Log of diamond drill hole D-5, Idaho Gulch 

A-6. Log of diamond drill hole D-6, Idaho Gulch 

A-7. Log of diamond drill hole D-7, Idaho Gulch 

A-8. Log of diamond drill hole D-8, Idaho Gulch 

A-9. Log of diamond drill hole D-9, Idaho Gulch 

B-1. Mineralogical analyses of magnetic fractions of samples representative of the regolith concentrates 

selected for SEM studies 



Page 
20 
20 
21 
21 
21 
21 
21 

24 



UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 



A 
cps 

ft 
ft^ 
ft^ 

ftVst 
G 

g 
in 



ampere 

count per second 

foot 

square foot 

cubic foot 

cubic foot per short ton 

gauss 

gram 

inch 



lb 


pound 


min 


minute 


mm 


millimeter 


pet 


percent 


ppm 


part per million 


s 


second 


st 


short ton 


wt pet 


weight percent 


yr 


year 



A COLUMBIUM-BEARING REGOLITH ON UPPER IDAHO GULCH, 

NEAR TOFTY, AK 



By J. Dean Warner,' C. L. Mardock,' and D. C. Dahlin^ 



ABSTRACT 



In 1984, as part of a project to evaluate Alaskan occurrences of certain critical and 
strategic minerals, the Bureau of Mines investigated a columbium-bearing regolith on 
upper Idaho Gulch, near Tofty, AK. The regolith is derived from weathering of a 
dolomitic marble and consists mostly of iron oxide minerals with accessory apatite, 
zircon, xenotime, rutile, monazite, and the columbium minerals aeschynite, columbite, 
and ilmenorutile. Two regolith lenses contain 340,000 lb of columbium resources at an 
average grade of 0.07 pet. Calculated composite concentrates from two regolith 
samples (approximately 200 lb each) contained 53 and 57 pet of the columbium at 
grades of 0.97 and 0.86 pet, respectively. In each case the grade could be improved to 
1.1 pet Cb with a sacrifice of 9-pct recovery. 

The regolith's mineralogy, trace-element geochemistry, and similarity to 
descriptions of other columbium-enriched regoliths suggest that the underlying 
marble may be a carbonatite. The lack of associated alkalic igneous rocks and the 
stratiform nature of the regolith, however, may be interpreted as evidence for 
sedimentary origin of the marble. The marble and regolith are a lode source for some of 
the minerals in the Idaho Gulch placer deposit. 

'Physical scientist, Alaska Field Operations Center, Bureau of Mines, Fairbanks, AK. 
-Geologist, Albany Research Center, Bureau of Mines, Albany, OR. 
'Metallurgist, Albany Research Center. 



INTRODUCTION 



In 1984, the Bureau of Mines investigated a co- 
lumbium-bearing regolith on upper Idaho Gulch, near 
Tofty, Hot Springs mining district, Alaska. The regolith is 
a residual weathering product of marble. It was originally 
identified in 1956 by the Bureau as a result of 
investigations to locate lode sources of tin, columbium, 
tantalum, chromium, and radioactive minerals found in 
placer gold deposits of the Tofty area. Approximately 
12,000 ft of trenching, comprising 40 trenches, and 1,400 
ft of diamond drilling were completed in the headwaters of 
Idaho Gulch at that time. The results of this early study, 
which were not published, indicated trace amounts of 
columbium and tantalum were present, but concluded 
that the regolith was not a lode source for heavy minerals 
found in placer deposits of the area. 

Conversely, the 1984 investigation indicates that 



uniformly low-grade concentrations and minor resources 
of columbium but no tantalum are present in the regolith. 
The regolith may represent residue overlying a carbon- 
atite and is a likely lode source for some of the heavy 
minerals occurring in the placer deposit on Idaho Gulch. 

This investigation was conducted as part of a Bureau 
project to assess Alaskan reserves or resources of certain 
critical and strategic minerals, including those containing 
columbium (1).^ The United States relies entirely on 
foreign sources of columbium, which is used mainly in 
heat- and corrosion-resistant alloys by the metallurgical 
and aerospace industries (2). The resources identified in 
this report represent approximately 6 pet of the United 
States annual demand for primary columbium (2). 

^Italic numbers in parentheses refer to items in the list of references 
preceding the appendixes at the end of this report. 



ACKNOWLEDGMENTS 



Although this report primarily presents results of 
recent investigations, it also incorporates and relies 
heavily on unpublished data generated by the 1956 
Bureau investigation in the Idaho Gulch area conducted 
by R. P. Maloney (deceased) and B. I. Thomas (retired). 
mining engineers with the Bureau of Mines. The report 
also benefited from discussions with D. M. Hopkins and R. 
M. Chapman, geologists with the U.S. Geological Survey, 
concerning the regional geology of the Tofty area. 



Discussion with D. T. Smith, geologist with the Alaska 
Division of Geological and Geophysical Surveys, helped 
clarify ideas about carbonatites. Field work was assisted 
by D. D. Southworth, graduate student. University of 
Alaska, Fairbanks, and by J. Y. Foley, physical scientist. 
Bureau of Mines, Fairbanks, AK. The logistical assistance 
of Robert Burgess, a placer miner at Tofty, is gratefully 
acknowledged. 



LOCATION AND ACCESSBILITY 



Tofty is located 95 miles west-northwest of Fairbanks. 
AK, about 15 miles northwest of the village of Manley Hot 
Springs, from which it is easily reached by gravel road 
(fig. 1). Manley Hot Springs is accessible by road or air 
throughout the year from Fairbanks and by river barge 



during the summer months from the railroad center at 
Nenana. The area investigated is located about 1.5 miles 
west of Tofty at the 800-ft elevation in Idaho Gulch. This 
area lies on the U.S. Geological Survey Tanana A-2 
quadrangle (1:63,360 scale). 




Figure 1 . — Location of study area. 



PHYSIOGRAPHY 



Tofty is located in the southwestern portion of the 
Yukon-Tanana upland physiographic division (3). near 
the confluence of the Yukon and Tanana Rivers. The 
terrain around Tofty is extremely subdued, characterized 
by gently sloping, northeast-trending hills, occasional 



subcircular rounded mountain tops, and broad asymmet- 
ric valleys (fig. 2). This area is entirely blanketed by 
vegetation and a thick mantle of perennially frozen loess 
covers all the valleys and lower portions of the hills. 




Figure 2.— Aerial view of Idaho Gulch showing trenches. 



LAND STATUS 



The Tofty area lies on Federal lands administered by 
the Bureau of Land Manaagement and is open to mineral 
entry. Ninety-five unpatented Federal placer mining 



claims cover most of the lower portions of the creeks near 
Tofty. The area investigated, however, was not claimed at 
the time of the investigation (August 1984). 



PREVIOUS INVESTIGATIONS 



Shortly after the discovery of gold in 1907, cassiterite 
(Sn02) was identified in placer concentrates from the 
Tofty area (4-6). Placer deposits containing cassiterite 
were found to lie within a northeast-trending belt, 
extending between Woodchopper Creek, to the southwest. 
and Cooney Creek, to the northeast, that informally 
became known as the Tofty tin belt (fig. 3). Subsequent 
studies of the tin-bearing placer deposits, spurred on by 
World War II and postwar tensions, were performed by 
Thome and Wright (7), Wayland (S), Thomas and 
Herdlick," and Thomas (9). No lode source of cassiterite 
has ever been reported. 

Columbium and rare-earth-element minerals have 
also been identified in placer concentrates from the Tofty 
tin belt. In 1934, Waters {10) identified the columbium 
mineral aeschynite |(Ce,Ca,Fe,Th) (Ti,Cb»2 (0,OH)fil, as 

'Preliminary investigations of tin and radioactive minerals in gold 
placer deposits near Tofty, Yukon River Region. Alaska iBM-4606-1. 
195oi. performed by the Bureau of Mines for the U.S. Atomic Energy 
Commission. 



well as zircon, pyrite, magnetite, ilmenite, monazite, 
xenotime, apatite, anatase, tourmaline, and barite in 
concentrate samples from placer mines on Deep Creek. 
Sullivan Creek, and Cache Creek. The identification of 
these minerals was confirmed by Moxham, in 1954, who 
also identified two previously unreported minerals, 
ellsworthite luranpyrochlore (U,Ca,Ce)2 (Cb,Ta)2 O^ 
(0H,F)1 and columbite |(Fe,Mn)(Cb,Ta)206l ill). Moxham 
found the greatest concentrations of the three columbium 
minerals and zircon and monazite in concentrates from 
placers on Idaho, Miller, and Harter Gulches. In 1955, The 
Bureau" confirmed Moxham's and reconfirmed Water's 
mineral identifications. The 1955 investigation also found 
from 0.2 to 7.0 pet Cb^Os in concentrates from test pits in 
tailings and from 0.15 to 1.8 pet Cb^Os, as well as 0.6 to 
0.25 pet Ce02, anomalous concentrations of lanthanum, 
and trace concentrations of yttrium in concentrates from 
churn drill holes on Miller and Idaho Gulches. 



''Work cited in footnote 5. 




LEGEND 

Op«n-pit ortot - lln btoring 

■ 1 > Oritl-iBin* ortot - fin btoring 

Protptctttf ortat - lln in4ieot(4 by 
cburn drilling an4 proiptct thofi 

' J Columblum-baarlng ragollth 

I 2 




V 



Hot Spring! 
Oonp 



Scalp, milti 

Figure 3. — Totty tin belt, Alaslca. 



In 1956, the Bureau, in an attempt to locate lode 
sources of the placer minerals, trenched on upper Idaho 
Gulch and identified two bodies of radioactive ferruginous 
regolith (figs. 2-3). Subsequent detailed sampling and 
diamond drilling defined two northwest-dipping, north- 
east-striking lenses of material containing trace amounts 
of columbium, phosphorus, and zirconium, among other 
metals, but no uranium, which was the principal interest 
of its study. The results of the lode investigations on Idaho 
Gulch were never published, but are partially incorpo- 
rated in this report. 



In 1984, as part of a current Bureau project to 
investigate critical and strategic minerals in Alaska, 
Southworth {12) reanalyzed concentrates from channel 
samples of tailings collected in 1956 by Thomas, for 
columbium. Southworth found that most samples con- 
tained between 0.2 pet and 4.5 pet Cb with higher values 
generally in gravels from the vicinity of Deep Creek, 
Miller Gulch, and Idaho Gulch. Using placer reserve 
figures from Thomas (9) and Wayland (8), Southworth 
calculated an inferred reserve of 100,000 lb Cb20-, within 
the Tofty placer deposits. 



BEDROCK GEOLOGY OF THE TOFTY AREA 



Bedrock outcrops in the Tofty area are rare; most 
geologic observations have been limited to now- 
inaccessible drift-mine exposures and sparse road cuts or 
inferred from placer cobble lithologies. In general, 
however, much of the area is underlain by a succession of 
graywacke, quartzite, siltstone, shale, slate, slaty argil- 
lite, and polymictic comglomerate that has been inter- 
preted as being a portion of a Mesozoic-age flysch basin 
that extends approximately 150 miles northeastward from 
the Tanana River to north of Livengood (13-16). These 



rocks exhibit local low grade (zeolite facies) metamorph- 
ism and severe deformation (17). Roadcut and trench 
exposures near Tofty and on Idaho Gulch show that 
bedding strikes east-northeast and dips moderately to 
steeply northwest; however, small hand-specimen to 
outcrop scale isoclinal folds are locally common. 

Minor amounts of serpentinized and chloritized 
ultramafic and mafic rock with locally associated graphi- 
tic slaty to schistose rock are exposed along the northwest 
margin of the flysch basin (13). These rocks may have 



either been tectonically emplaced or partially intruded 
within the basal flysch unit. Alternatively, some of the 
ultramafic, mafic, and metasedimentary rocks may under- 
lie the flysch and be exposed in erosional windows. 

Magnetite-apatite bearing limestone, similar to that 
identified on upper Idaho Gulch in this report, is described 
by Wayland on Harter Gulch (8). The relationship of this 
rock to other units is unknown; carbonate rocks are not 
reported elsewhere within the flysch belt. 

The Mesozoic flysch is cut by two intrusions in the 



Tofty area. A biotite granite pluton with local felsic 
segregations and associated tourmaline crops out on Hot 
Springs Dome, southeast of Tofty, and a monzonite and 
quartz-monozonite composite pluton crops out on Rough- 
top Mountain, northeast of Tofty (fig. 3). The intrusion on 
Roughtop Mountain shows a Late Cretaceous radiometric 
age of 92 ± 10 million yr, the intrusion on Hot Springs 
Dome has an early Tertiary radiometric are of 62 ± 3 
million yr (13). 



NATURE AND EXTENT OF PRESENT INVESTIGATIONS 



During this investigation, data from nine trenches 
and nine diamond drill holes compiled by the Bureau in 
1956 were reevaluated. The reevaluation comprised 
reanalyses of available samples, selective reexcavation of 
the trenches, and relogging of available core. Information 
resulting from the 1956 investigation is presented and 
acknowledged where appropriate. Figure 4 shows loca- 
tions of trenches and drill holes and mapped extent of the 
regolith. Modified 1956 drill logs and geologic cross 



sections constructed from drill data are presented in 
appendix A. 

Additional methods used during this study include 
selective sampling of the 1956 trenches; optical, radiomet- 
ric, scanning electron microscope (SEM), microprobe, and 
X-ray diffraction (XRD) studies of mineral compositions; 
and magnetic, radiometric, and soil sampling surveys over 
a 500- by 1,900-ft grid area (outlined on figure 4). 




no 200 

1 1 1 


T-l 
« > 


LEGEND 
Tronch and dump 


Scala.fMt 
Contour Innrvol 20 (Mt 


/ 


1 1 


Ragollth 


/ 


•0-S 


DKXTKXKl drill hoi* 



/ 



Figure 4.— Locations of trenches and drill holes and mapped extent of the regolith. 



GEOLOGY OF THE REGOLITH 



Two bodies of iron-rich regolith were identified on 
upper Idaho Gulch by Bureau trenching in 1956. 
Subsequent drilling indicated the regolith forms conform- 
able lenses within the N 60° E trending wallrock units. 
The lenses grade downward into, and apparently have 
been derived by chemical weathering of dolomitic marble 
(figs. A-1 — A-6). In plan view, both lenses are irregular in 
shape, varying in thickness from 3 to 80 ft. The 



northwestern lens is partially exposed by trenching over a 
strike length of 620 ft and dips approximately 50° to the 
northwest (fig. A-6). The southeastern lens is partially 
exposed over about 350 ft of strike length and dips 
between 40° and 50° northwest (figs. A-1— A-4). In 1956, 
both lenses were mapped as pinching out to the southwest, 
but open ended to the northeast (fig. 4). 

Cross sections in figures A-1 through A-5 show that 



the southeastern regolith lens ranges in thickness from 17 
to 28 ft, averaging 23 ft at trench T-8, and persists 
downdip for between 100 and 250 ft. The regohth, where 
intersected approximately 100 ft downdip in drill holes 
D-9, D-1, and D-6, has true thicknesses of 12, 16, and 23 ft, 
respectively. The increase in drill-intersected thicknesses 
suggests that the southeastern regolith lens may be 
thicker and extend deeper northeast of the trenches and 
diamond drill holes. 

The northwestern regolith lens is approximately 31 ft 
thick at trench T-6 but is of unknown thickness at 
distances less than 200 ft downdip (fig. A-6). Where 
intersected at 200 ft downdip in drill hole D-3, the 
northwestern regolith lens consists of thin, discontinuous 
zones in dolomitic marble. 

The footwall of the regolith grades into marble at 
distances of as little as 50 ft downdip in some drill holes; 
the regolith is generally absent at distances greater than 
200 ft downdip (figs. A-3 and A-6). Because both the 
hanging wall and footwall were only observed in drill hole 
D-3, the attitude and shape of the marble body is 
unknown. 

The marble consists of coarse, granular ankeritic 
(composition determined by XRD analysis) dolomite and 



calcite with up to 10 pet disseminated and banded rounded 
magnetite and euhdral to rounded pyrite grains and up to 
5 pet disseminated rounded apatite crystals. In this rock, 
pyrite commonly replaces magnetite. Minor amounts of 
biotite, some of which is partially replaced by chlorite, are 
also present and a trace amount of zircon occurs. 

Drilling and trenching indicate the regolith and 
marble occur within a succession of probable intermediate 
grade (greenschist facies) metasedimentary and metaig- 
neous(?) rocks consisting of variable amounts of quartz, 
muscovite, sericite, chlorite, and graphite and locally 
minor amounts of talc, serpentine, dolomite, calcite, 
magnetite, or pyrite. Lack of outcrop and poor core 
recovery from drilling preclude detailed correlations 
between the various rock types. In general, however, the 
footwalls and lower few feet of the hanging walls of both 
regolith lenses consist of calcareous chlorite-sericite ± 
talc ± quartz phyllite and schist and the section of 
hanging wall beginning a few feet above each lens consists 
of siliceous muscovite-graphite schist (cross sections A-2, 
A-3, and A-5 through A-7, appendix A). The footwall of the 
regolith lens in drill hole D-7 consists of a nonfoliated 
chlorite-sericite-quartz rock that may represent a meta- 
morphosed mafic igneous rock. 



MINERALOGY AND PETROGRAPHY OF THE REGOLITH 



Most of the regolith consists of a moderate amount of 
pebble- to cobble-size rock fragments in a dark chocolate 
brown to brownish orange earthy matrix composed largely 
of sooty and specular hematite, exotic limonite, small 
fragments of limonitic boxworks after pyrite, goethite, 
and hematitic magnetite. 

The most common rock type consists of a dark red 
spongelike matrix of siliceous hematite with up to 40 pet 
rounded to angular 0.5- to 2-mm apatite grains and trace 
amounts of euhedral zircon crystals. Cross-cutting vein- 
lets of goethite and chalcedony and patches of limonitic 
boxworks after pyrite are also common. This hematite- 
rich rock grades into a less common, more siliceous rock 
consisting of up to 40 pet euhedral to broken subhedral 
and finer rounded apatite and irregularly shaped hemati- 
tic magnetite grains with minor euhedral to angular 
zircon crystals or fragments in a matrix of iron-stained 
finely crystalline quartz. Rounded grains of carbonate, 
chert, and chlorite schist (?) also occur as inclusions in this 
rock. 

Other rocks found in the regolith include massive 
vuggy goethite and yellowish-orange porous limonite 
within which are rounded fragments of kaolinitized 
phyllite(?) and veinlets of goethite, hematite, quartz, 
chalcedony, carbonate, and apatite. 



Near its wallroek contacts, the regolith is more 
yellow-orange in color and is composed mostly of limonitic 
clay. Secondary(?) apatite occurs as bluish gray to white 
botryoidal masses along fractures in fragments of earthy, 
porous limonite in these areas. An apple-green clay 
containing a chromiferous member of the montmorilli- 
nite-beidellite series and possible traces of anatase' is 
associated with limonitic kaolinite in the footwall of the 
southeastern regolith lens in trench T-8. 

Geochemical, radiometric, optical microscope, micro- 
probe, and SEM examination of the minus 20-mesh 
fraction of concentrates panned from regolith samples** 
indicate the regolith also contains trace to minor amounts 
of apatite, zircon, monazite, xenotime, brewsterite(?), 
columbium-bearing rutile, which may locally alter to 
ilmenorutile, and the columbium minerals aeschynite 
and columbite. Results of analyses of concentrate samples 
are presented in table 1, and ranges of mineral content in 
samples are listed in table 2. Apatite occurs as fine 
bluish-white grains with a composition (determined by 
XRD analysis) intermediate between the hydroxyl 



"Identification of anatase and clay minerals in 1956 by H. D. Hess, 
formerly of the Bureau of Mines, Albany, OR. 

"A test procedure for characterization of the Tofty regolith concentrates 
is described in appendix B. 



Table 1. — Results of analyses' of samples of pan-concentrated regolith, parts per million 



Sample^ 


Cb 


Sn 


Ta 


Ce 


La 


Nd 


Y 


Description 


5 

9 

15 

30 


5,700 

9,000 

100 

300 


<50 
<50 
<50 
<50 


<100 

100 

<100 

<100 


1,000 

1,000 

ND 

ND 


400 
400 
ND 
200 


<500 

<500 

ND 

ND 


<10 
20 

<10 
ND 


Heaping pan reduced to 10.6 g. 
Heaping pan reduced to 29.4 g. 
Heaping pan reduced to 20.4 g. 
2 heaping pans reduced to 34.7 g. 



ND Not detected. 

'Cb, Sn, and Ta analyses by X-ray fluorescence; Ce, La, Nd, and Y analyses by emission spectrography (other rare-earth 
elements not detected). Analyses by the Bureau's Reno Research Center, Reno, NV. 

^Samples are numbered clockwise starting with trench T-2. Gaps between sample numbers listed here correspond to samples 
listed in tables 3 and 4. 





Figure 5. — Scanning electron microscope photomicrograph (A) and columbium X-ray scan (B) of cotumbium-rlch portion of 
regolith concentrate. 



Table 2. — Estimated ranges for mineral content in minus 

20-mesh fraction of samples of pan-concentrated regolith,' 

weight percent 



Mineral 

Goethite 30-40 

Quartz 11-16 

Aeschynite 7-9 

Magnetite 8-10 

Rutile (Cb-bearing) 4-6 

Zircon 6-15 

Fe-Mg silicates 1-5 

Tr Trace. 

'Samples 5. 9, 15, and 30. 



Mineral 

Feldspar 1-4 

Monazite 2-4 

Columbite 2-4 

Xenotime Tr 

Brewsterite (?) Tr 

Apatite Tr 

Rock fragments Tr 



(Ca5(P04)30H) and fluor (Ca5(P04).sF) endmembers of the 
apatite solid solution series. Although apatite is locally 
abundant in the regolith, its relatively low specific gravity 
makes it a rare constituent of the concentrates. Zircon 
occurs as 0.1- to 0.5-mm, clear euhedral and yellowish 
subhedral bipyramidal crystals or crystal fragments with 
poorly developed prism faces. Microanalysis indicates 
monazite to be of the high-cerium and high-lanthanum 
and low-yttrium and low-thorium variety and locally 
intergrown with columbite. 

An SEM photomicrograph and columbium X-ray scan 
of the columbium-bearing portion of a regolith concen- 
trate is shown in figure 5. Aeschynite occurs as dark 
reddish brown to black, approximately 0.1-mm angular, 
flattened prismatic orthorhombic crystals with a general 
composition, based on four analyses, of (Cao ^.-i-o.iu Feo.os- 




Figure 6. — Scanning electron microscope photomicrograph 
of broken aeschynite grain from regolith concentrate. 



0.46 Ceoo4-n.27 Mno.0.0.3 Bao-o.os Tho.0.14 Ago.0.14* 'Cbo.53-Q.90 
Ti(), 10-0.47 '-iOfi- Aeschynite is the bright phase in figure 5A 
with the less intense columbium signals in figure 5B; a 
closeup of the aeschynite is shown in figure 6. Columbite 
is also a bright phase in figure 5A, but has the more 
intense columbite signals in figure 5B. The columbite is 
the high-iron, low-manganese variety and has a composi- 
tion of (Feo.9 Mno.o9 Cao.oi) (Cbo.95 Tio.o5)206- 



REGOLITH SAMPLING 



METHODS AND RESULTS 



In 1984, samples of regolith and specimens of rocks 
were collected from trenches on upper Idaho Gulch for 
geochemical analyses. The wider trenches, T-5 and T-8, 
were mapped and sampled in detail (figs. 7-8). Vegetation 
cover and sloughing of trench walls prevented detailed 
mapping and sampling of other trenches; only a few 
samples were collected from trenches T-2, T-3, and T-4 
(fig. 9). 

LEGEND 




Hemotiiic regoliih 

I I Limonjtic regolith 

r . 1 undifferentioied melosedimentory 
rocks 

Geologic conioct; hochured where 
grodotionol 

cm Trench 

C5i6 "'Solith lomple pit 

# 14 Rock specimen 

O 15 Concenirote sample 



Figure 7. — Locations of samples collected in trench T-5. 



Regolith samples were collected from 3- to 4-ft-deep 
pits (figs. 7-9). One pit was excavated in each of trenches 
T-2, T-3, and T-4 and a series of pits were dug in each of 
trenches T-5 and T-8. A vertical channel sample and a 
bottom sample were collected from each pit. 

Regolith samples and rock specimens were crushed, 
split, pulverized, and analyzed by the Bureau's Reno (NV) 
Research Center. Regolith samples were analyzed for 
columbium, phosphate (P20,-,l, zirconium, and zinc by 
X-ray fluorescence (XRF), tin by atomic absorption (AA), 
and 42 elements plus rare-earth elements by emission 
spectrography. Results and methods of analyses are 
presented in tables 3 and 4 and appendix C. Owing to the 
sensitivity of the analytical techniques used, some 
variations exist among the results presented for some 
individual samples. 

Samples of regolith collected from pits in trenches 
T-2, T-3, T-4, T-5, and T-8 contain <50 to 1,200 ppm Cb, 
0.14 to 21.4 pet P2O5, <100 to 900 ppm Zr, 200 to 1,200 
ppm Zn, and not detected to 900 ppm La (table 3). Low 
columbium values in samples from the pit in trench T-3 
are likely not representative of regolith as their yellow- 
white color suggests that sloughed bank material was 
included in the samples. 

Regolith samples also contain 0.07 to >6 pet Ba, 7 to 
>10 pet Fe, 0.3 to >10 pet Mn, 3 to 4,000 ppm Sr, 2,000 to 
20,000 ppm Ti, 50 to 6,000 ppm Cr, and 100 to 3,000 ppm 
Ni (appendix C). Relatively higher values of columbium, 
phosphate, zirconium, lanthanum, and strontium are 
restricted to samples from pits excavated in the red-brown 



LEGEND 



Hematitic regolith 

Limonitic regolith 

Undifferentiated meto- 
sedimentary rocks 



^,„. Geologic contoct; hochured 
where grodotionol 



C .' .' ^ Trench and dump 
C2> 22 Regolith sample pit 
Rock specimen 



31 



v30 



Concentrate sample 




25 

I 



50 

J 



Scole, feet 




Figure 8. — Locations of samples collected in trench T-8. 



T-2 





/ 



/ 



LEGEND 

Undifferentiated regolith 

Undifferentioted metosedi- 
mentary rockt 

Geologic contaci 

Trench and dump 

Regolith sample pit 

Rock specimen 

Concentrate sample 

Dump sample 



Figure 9.— Locations of samples collected in trenches T-2, T-3, and T-4. 



Table 3. — Results of XRF analyses^ of regolith samples, in parts per million except as noted 



Sample 


Cb 


La^ 


P^Os^ 


Zr 


Zn 


Sample type and/or description 


TRENCH T-2 


1 

2- 

3" 


<50 

1.000 
1,200 


NA 

NA 
NA 


0.19 

1.95 
2.03 


300 

800 

800 


NA 

NA 
NA 


3-ft channel of dump, material is well mixed 

and silty. 
From bottom of pit, hematitic regolith. 
3.5-ft vertical channel in sample 2 pit. 


TRENCH T-3 


6" 

7" 

8 


72 

<50 
<50 


NA 

NA 
NA 


NA 

NA 
0.14 


NA 

NA 
300 


NA 

NA 
NA 


From bottom of pit, includes sloughed bank 

material, 
3-ft vertical channel in sample 6 pit. 
3-ft-long, 10-in-deep channel of dump. 


TRENCH T-4 


11 


300 
600 

500 


200 
400 

200 


0.82 

11.7 

7.3 


400 
700 

900 


400 
600 

300 


4.5-ft-long, 1-ft-deep channel of dump. 
From bottom of pit, hematitic regolith. Bulk 

sample A^ collected from this pit. 
3.5-ft vertical channel in sample 12 pit. 


12" 

13 


TRENCH T-5 



16 <50 ND 0.17 <100 500 

17 <50 ND .26 200 400 

18 1,000 900 7.1 900 300 

19 700 400 .5 800 300 

20 100 ND .8 300 300 

TRENCH T-8 

22 300 ND 9.0 700 400 

23 400 • ND 8.1 700 400 

24 500 ND 112 200 600 

25 700 200 1 .68 400 500 

26 1,000 400 10.4 800 300 

27 700 200 10.4 700 400 

28 <50 NA .26 300 200 

29 <50 NA 94 <100 250 

32 300 ND 90 100 1,200 

33 400 40 2.60 500 900 

34 800 90 1.92 500 1,100 

35 900 90 1.79 700 1,100 

36 300 400 21 .4 900 300 

37 300 200 20.4 900 300 

38 <50 ND .79 200 200 

39 100 ND 1 .47 200 300 

40 58 ND 69 200 400 

41 100 ND 1.06 300 500 

NA Not analyzed ND Not detected. 

'Performed by the Bureau's Reno Research Center, Reno. NV; Sn analyzed by AA, but not detected. 
^No other rare-earth elements detected in samples, except sample 36 contains 40 ppm Y Analyses by em; 
^Percent. 

"Samples 2, 3,6,7, and 1 2 also contain 2.083, 2.445, 0.05, 0.06, and 1 07 ppm Au and 1 .431 . 1 .528, 1 6, 4 
Ag values at or below detection limit. Au and Ag determined by inductively coupled plasma analyses. 
^Head analysis of 0.093 pet Cb. 
^Head analysis of 0. 1 20 Cb. 



From bottom of pit, limonitic regolith. 
4-ft vertical channel in sample 16 pit. 
From bottom of pit, hematitic regolith. Bulk 

sample B^ collected from this pit. 
4-ft vertical channel in sample 18 pit. 
Sample of clay from adjacent to footwall of 

limonitic regolith. 



From bottom of pit, hematitic regolith. 
4-ft vertical channel in sample 22 pit. 
From bottom of pit, hematitic regolith. 
3-ft vertical channel in sample 24 pit. 
From bottom of pit, hematitic regolith. 
3-ft vertical channel in sample 26 pit. 
1.5-ft channel of limonitic clay-rich regolith. 
Composite of top 1 ft of sample 28 pit. 
From bottom of pit, hematitic regolith. 
3-ft vertical channel in sample 32 pit. 
From bottom of pit, hematitic regolith. 
3.5-ft vertical channel in sample 34 pit. 
From bottom of pit, hematitic regolith. 
2.5-ft vertical channel in sample 36 pit. 
From bottom of pit in graphite phyllite. 
Channel in limonitic clay-rich regolith above 

sample 38. 
From bottom of pit. 
2.5-ft vertical channel in sample 40 pit. 



ssion spectrography, Reno Research Center. 
0, and 'iO.3 ppm Ag, respectively. All other Au and 



10 



Table 4. — Results of analyses,' in parts per million, and descriptions of rock specimens 

Sample Cb Sn Ta Au Ag Ce La Y Description 

4 <100 <50 <100 <0.007 <0.3 ND ND ND 10 pet rounded to angular apatite grains within matrix 

of siliceous iron oxides. Cut by chalcedony veinlets. 

10 200 <50 <100 .016 .370 ND ND -10 Grab from dump. Mostly red-brown earthy hematite 

14 <100 <50 <100 <,007 <.3 ND ND <10 Orange, limonite-rich clay. Grab sample. 

21 1,200 <50 <100 <.007 <.3 ND 400 20 Earthy, hematitic matrix cut by chalcedony veinlets. 

Representative of rocks in trench T-5. 
31 200 <50 <100 <.007 <.3 ND 200 -10 4 pet rounded weathered apatite in a dark red earthy 

hematitic matrix cut by veinlets of goethite. 
42 <100 <50 <100 <.007 <.3 ND 90 20 Dark, angular maroon-colored patches in a punky 

limonitic matrix. Disseminated magnetite blebs also 

present. 
43 300 <50 <100 <.007 <.3 2,000 900 20 Rounded quartz grains in a weathered limonitic matrix. 

Cut by veinlets of quartz, carbonate, and secondary 

apatite. 
44 200 <50 <100 <.007 <.3 ND 40 40 Dark-red to orange siliceous iron oxide matrix cut by 

some veinlets of drusy quartz. 
45 700 <50 <100 NA NA ND 200 20 Blebs of limonile and magnetite in an iron-stained 

siliceous matrix. 
46 400 <5 NA 0.007 0.3 <500 90 40 40 pet euhedral to angular subhedral and finer rounded 

apatite, irregular to rounded magnetite, and minor 

euhedral zircon in an iron-stained siliceous matrix. 
47 200 <5 NA <,007 <.3 <500 90 40 Rounded apatite and hematite-magnetite grains, minor 

angular zircon crystals, and rare fragments of chert 

or schist (?) in a matnx of coarse recrystallized 

quartz and Iron oxides. 
48 200 <5 NA .020 894 <500 200 40 Massive fine exotic limonite with rounded 3- to 7-mm 

fragments of clay after phyllite (?), cut by veinlets of 

goethite. 
49 87 <5 NA <.007 <.3 <500 ND 40 5 pet rounded apatite grains in a punky siliceous 

hematite matrix cut by veinlets of goethite. 
50 <50 9.1 NA <.007 <.3 <500 ND 40 Massive vuggy goethite. 

NA Not analyzed, ND Not detected. 

'Cb and Ta analyses by XRF; Sn by AA (5-ppm detection limit) or XRF (50-ppm detection limit): Au and Ag analyses by inductively coupled plasma analyses. 
Rare-earth analyses by emission spectrography — only Ce, La, and Y detected except sample 42 also contained 1,000 ppm Nd. Analyses by the Bureau's Reno 
Research Center, Reno, NV. 



hematitic regolith whereas a small number of high values 
of zinc, titanium, barium, chromium, and nickel are 
present in samples collected from both the hematitic 
regolith and yellow-orange limonitic regolith. 

Rock specimen sample locations are also shown in 
figures 7, 8, and 9. Because specimens were generally 
collected from float, analyses are interpreted to be 
representative only of the specimen and not the deposit 
grade. Ten of fourteen specimens contained between 200 
and 1,200 ppm Cb with traces of cerium, lanthanum, 
yttrium, or silver; three samples contained traces of gold 
and one sample contained detectable concentrations of tin; 
no tantalum was detected (table 4). The highest co- 
lumbium concentration (1,200 ppm) was found in a 
specimen of earthy hematite cut by chalcedony veinlets. 

Results of analyses for columbium in channel samples 
collected in 1956 from trench T-8 are presented in table 5 
and sample locations are shown in figure 10. The analyses 
are in good agreement with those from samples collected 
from pits in 1984 and generally range between 300 and 
700 ppm Cb with one value of 200 ppm and one of 1,000 
ppm. 

Results of columbium analyses in 1956 of sludge 
samples of regolith from drill holes are presented in table 
6. Similar to results of analyses of samples from trenches, 
between 0,01 and 0.10 pet Cb was detected in all samples. 

Results of analyses of three composite samples of 
marble from drill hole D-4 are presented in table 7. 
Between 257 and 731 ppm Cb as well as elevated 
concentrations of phosphate, lanthanum, zirconium, and 
cerium are present in the samples. These columbium 
concentrations are very similar to those found in samples 
of regolith. Unfortunately, no other drill core containing 
marble is available for analyses. 



Table 5. — Results of XRF analyses' for columbium in channel 
samples collected from trench T-8 in 1956 





Cb, 


Channel 




Cb, 


Channel 


Sample 


ppm 


length, ft 


Sample 


ppm 


length, ft 


51 


300 


8.8 


61^ 


. 700 


6.3 


52 


600 


9.5 


62 


. 400 


7.3 


53 


400 


7.0 


63 


. 300 


10.4 


54 


300 


9.3 


64 


. 300 


6.9 


55 


200 


10.0 


65 


. 300 


9.95 


56 


400 


7.4 


66 


. 400 


9.80 


57 


. 300 


7.4 


67 


. 300 


13.00 


58 


400 


5.8 


68 


. 700 


8.80 


59 


300 


7.5 


69 


400 


7.60 


60^ 


1,000 


6.3 









'Performed by Bureau's Reno Research Center, Reno, NV, in 1984. 
^Analysis by unspecified chemical techniques in 1956. 

Table 6.— Results of 1956 emission spectrograph ic (S) and 

chemical (C) analyses' for columbium in sludge samples of 

regolith 





Drill hole 


Interval, ft 


Cb, pet 






S 


C 


n-1 




133.2-138.1 

138.1-143.3 

6.8- 19.3 

70.0- 89.4 


0.01-0.10 
.01- .10 
.01- .10 
.01- .10 


<0.1 


D-7 




<.1 
<.1 


n-Q 




NA 









NA Not analyzed. 

'Analyses performed by Bureau's Reno Research Center, Reno, NV. 

Table 7.— Results of analyses' of composite samples of 
marble from drill hole D-4, parts per million except as noted 



Sample 


Interval, ft 


PaOs^ 


Cb 


La 


Zr 


Y 


Ce 


70 

71 

72 


174-196 
196-225 
225-245 


1.32 
1.86 
2.74 


257 
731 
416 


327 
219 
927 


653 
190 
277 


21 
21 
26 


529 

373 

1472 



'P2O5 analyzed by emission spectrography, other elements by XRF; 
performed by Bondar-Clegg, Lakewood, CO. 
^Percent. 



11 




LEGEND 

C. ; ; j^ Trench and dunnp 
I 53 Channel sample 



25 



50 



Scale, feet 




Figure 10. — Locations of 1956 channel samples in trench T-8. 



INTERPRETATION 

The average grade of the hematitic regolith on upper 
Idaho Gulch is probably between 0.04 and 0.07 pet Cb. 
Channel samples from trench T-8 contain from 200 to 
1,000 ppm Cb. The weighted average of those values is 
0.04 pet Cb over 160 ft comprising six channel samples 
with lengths varying from 19.9 to 39.2 ft. Sixteen of 
eighteen samples collected from pits in the hematite-rich 
portions of the regolith contain between 300 and 1.200 
ppm Cb and average approximately 725 ppm Cb; 12 of 
these samples contain columbium in excess of or equal to 
500 ppm. Spectrographic and chemical analyses per- 
formed in 1956 also show between 0.01 and 0.10 pet Cb in 
drill hole sludge samples of regolith. Columbium values 
similar to those in the hematitic regolith samples are also 
present in samples of marble. 



In contrast, five of nine samples collected from pits in 
clay-rich limonitic regolith contain less than 50 ppm Cb 
and the remaining four samples contain from 50 to 100 
ppm Cb. 

The presence of columbium and the mineralogic 
similarities between rock specimens and regolith suggest 
that the specimens are essentially undecomposed or 
silicified equivalents of the regolith. Many of these rocks 
fit the description of "boulders of cellular iron-stained 
apatite-rich material" at Magnet Cove, AR, which is a 
well-studied, columbium-bearing carbonatite deposit (18, 
p. 43). At Magnet Cove, rocks with mineralogy and fabric 
similar to those in the regolith on Idaho Gulch grade 
downward into a magnetite-apatite-perovskite-bearing 
marble that contains approximately 300 to 400 ppm Cb. 
These values are very similar to those found in the marble 
on Idaho Gulch (table 7). 



12 



MAGNETIC, RADIOMETRIC, AND SOIL SAMPLE SURVEYS ON UPPER IDAHO GULCH 



METHODS AND RESULTS 

Magnetic, radiometric, and soil sample surveys were 
conducted over the area known, or projected, to overlie 
ferruginous regolith on upper Idaho Gulch (fig. 4). 
Magnetic and radiometric measurements were taken at 
25-ft intervals on 17 northwest-trending 500- to 900-ft- 
long lines spaced 100 to 200 ft apart. Soil samples were 
collected at 25-ft intervals on seven 500-ft-long lines 
spaced 200 ft apart. Survey lines are oriented N 30 W, 
perpendicular to the trend of the regolith lenses. Figures 
11, 12, and 13 are contour maps showing the results of the 
three surveys. Results are also tabulated in appendix D. 

The magnetic survey was performed using a Geomet- 
ries UniMag 11, model G-846 portable proton 
magnetometer. ' Measurements were corrected for diurnal 
variations with time-variation graphs constructed from 
repeated measurements at a single station. All measure- 
ments were taken facing N 30 W, perpendicular to the 
strike of the regolith lenses. 

High concentrations of magnetite in the regolith 
produce strong positive magnetic responses. At intensities 
above 56,600 gammas, two 1,200-ft-long, N 60 E-trending 
areas, which merge to the southwest, are defined (fig. 11 ). 
Magnetic profiles are generally asymmetric, with steep 
positive slopes to the southeast and gentle negative slopes 
to the northwest. Peak magnetic intensities are offset to 
the northwest of the regolith, correlating with the 
northerly dip of the lenses. 

Total-count gamma-ray radiation was measured 
using a Scintrex model G15-5 gamma-ray spectrometer. 
Measurements were taken at hip level over 10-s intervals. 
Trace amounts of radioactive minerals, including zircon, 
monazite, apatite, and aeschynite, in the regolith produce 
radiation measurements between 100 and 250 cps in 
trenched areas (fig. 12). Two larger irregularly shaped 
northeast-trending and six other smaller areas with 
higher radiation values were delineated. 

Soil samples were collected at depths of 2.5 to 3.0 ft 
with a hand auger. Approximately 0.5 lb of sample 
material was placed in a paper envelope, dried, and 
screened to minus 80 mesh. Samples were analyzed by the 
Bureau's Reno (NV) Research Center for columbium, 
P2O5, and zinc by X-ray fluorescence. 

Most soil samples consisted of gray-brown, clay-rich 
silt, but some also contained limonite and rock fragments 
and were yellow-orange to red. Organic contents of 



^Reference to specific products does not imply endorsement by the 
Bureau of Mines. 



samples ranged widely, but generally were low. Much of 
the soil in the surveyed area is windblown silt without a 
developed profile, however some of the samples containing 
rock chips or hematite staining may contain residual 
material derived from bedrock. 

Drilling and a test pit at the midpoint of soil sample 
line 10,000 NE show that the silt ranges from 3 to 9 ft and 
averages approximately 5 ft in thickness. The presence of 
rare bedrock outcrops near Idaho Gulch suggests that the 
silt cover thickens away from the gulch. 

The large concentrations of apatite in the regolith are 
reflected by soil samples with anomalously high P2O5 
concentrations. P2O5 soil values above a threshold of 
0.3 pet define two 25- to 125-ft-wide anomalous areas that 
are coincident with and extend beyond the known extent 
of the regolith (fig. 13). 

In contrast to P2O5 concentrations, anomalously large 
columbium or zinc concentrations were limited to samples 
that were collected either from trenched areas or that 
contained iron-stained material derived from buried 
regolith. Five of seven detected columbium values occur 
within samples collected from regolith exposed in tren- 
ches; the other two samples were noteworthy for their 
orange-red color. Zinc values above 240 ppm also are 
limited to samples collected from trenched areas or that 
contain iron-staining derived from regolith. 



INTERPRETATION 

The magnetic, radiometric, and soil sample surveys 
produced complementary results indicating that the two 
regolith lenses extend along strike for approximately 
1,200 ft. The two lenses may join to the southwest. 
Asymmetric magnetic responses offset from the surface 
expression of the regolith suggest a moderate to steep 
northwest dip of the two lenses. 

Comparison of the data indicates that soil P2O5 
concentrations define the area underlain by regolith 
better than does radiation, but neither defines the extent 
of the regolith as well as its magnetic signature. Higher 
radioactivity is generally restricted to exposed portions of 
the regolith. 

It is likely that away from the trenched areas and 
Idaho Gulch, all three surveys were seriously hindered in 
detecting the regolith by the greater thicknesses of silt 
cover. There is good probability that the lenses may 
continue undetected along strike, especially to the 
northeast. 



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16 



COLUMBIUM RESOURCES 



Approximately 340.000 lb of indicated and inferred 
columbium resources are present within the known and 
inferred extent of the regolith lenses on uper Idaho Gulch. 
According to standard guidelines, set by Bureau of Mines 
and U.S. Geological Survey il9), this columbium compris- 
es approximately 30,000 lb of indicated and approximate- 
ly 310,000 lb of inferred resources. 

The indicated resource comprises that portion of the 
southeastern regolith lens exposed in trench T-8 and 
intersected in drill holes D-1. D-2, D-3, D-6, D-7, and D-8. 
Drill hole intersections show that this lens decreases from 
an average thickness of 23 ft at the surface to an 
approximate average of 17 ft at 100 ft downdip. Given 
the 6.900 ft- surface area and 40" north dip of the 
hematitic regolith in trench T-8. and assuming that the 
average thickness decreases by 50 pet at 150 ft downdip. 
the volume of hematitic regolith represented by that 
exposed in trench T-8 is approximately 500,000 ft". At a 
measured' tonnage factor of 23.5 ft st and a minimum 
grade of 0.07 pet Cb," a minimum of approximately 30,000 
lb of indicated resource is present. 

The inferred columbium resource comprises the 
remaining known or projected regolith. The average 



'"Tonnage factor determined on dried, compacted material: all analyses 
are also on a dry basis. 

"The average grade was determined previously in the text to be between 
0.04 and 0.07 pet Cb. Head analyses of 0.12 and 0.093 pet Cb on two 200-lb 
samples of the regolith suggest the higher value may be more accurate. 



apparent thickness, as measured in trenches, over the 
remaining 2,200 ft of strike length is approximately 50 ft. 
Subtracting 40 pet of this to account for an approximate 
average amount of unmineralized limonitic regolith, and 
given an approximately 45° northerly dip of the regolith 
lenses, the average true thickness is 22 ft. Assuming a 
weathering pattern similar to that in trench T-8 where 
the regolith decreases in thickness by 50 pet at 150 ft 
downdip, then the volume of inferred hematitic regolith is 
approximately 5.25 million ft'. At a tonnage factor of 23.5 
and a grade of 0.07 pet Cb, a minimum of approximately 
310,000 lb of inferred columbium resource is present. 

The regolith also contains zirconium and P2O5 
resources. Seven of eight 1984 channel samples collected 
in pits contain 700 to 900 ppm Zr (table 3). At an average 
concentration of approximately 0.07 pet Zr and a total 
regolith tonnage of approximately 245,000 st, an inferred 
zirconium resource is approximately 340,000 lb. P2O5 
values in the same eight samples range from 0.5 to 20.4 
pet. The average of these values is 6.5 pet P2O5; 
discounting the high and low values, the average is 5.2 pet 
FoO.T. At a concentration of 5 pet P2O5 and a total regolith 
tonnage of 245,000 st, an inferred P2O5 resource is 
approximately 12,250 st. 

Good potential also exists for large additional 
resources of columbium in the dolomitie marble under- 
lying the regolith. At an average grade similar to that of 
the regolith, the marble may contain several times the 
identified resource. 



BENEFICIATiON OF COLUMBIUM FROM THE REGOLITH 



Two large bulk samples of regolith, each weighing 
approximately 200 lb, were collected from trenches on 
upper Idaho Gulch for columbium beneficiation studies. 
Sample A was collected from trench T-4 from the same pit 
as samples 12 and 13 and had a head analysis of 0.09 pet 
Cb. Sample B was collected from trench T-5 from the same 
pit as samples 18 and 19 and had a head analysis of 0.12 
pet Cb. 

Figure 14 illustrates the procedure used to beneficiate 
the two samples. The samples were screened and ground 
in stages to pass 65 mesh and then tabled on a slime deck 
to produce a rougher concentrate, coarse tailings (those 
that settled and banded on the deck), and fine tailings 
(those that washed off the deck without settling). The 
rougher coarse tailings were screened and reground in 
stages to pass 150 mesh and then re tabled in a scavenger 
step. A scavenger concentrate, coarse tailings, and fine 
tailings were produced. The rougher and scavenger 
concentrates were combined and scrubbed at 50 pet solids 
for 10 min in a 1:2 volume HCI-H2O solution (13 pet HCl 
by weight) to remove iron oxide staining from the mineral 
surfaces. The scrubbed concentrate was washed and 
decanted four times and then treated by magnetic 
separation. A hand magnet was used to remove magnetite 
and other highly magnetic material. The remainder was 
slurred and pumped through a high-intensity wet magne- 
tic separator with a grooved-plate configuration at eight 
power settings. The magnetic field strength varied from 
approximately 500 G with the hand magnet to about 9,500 
G at the maximum power setting. 





Screening 


Sample 

1 

and grinding (minus 


65 mesh) 








\ 

Rougher tabling 






r- Concentrate 


Screening 


Coarse tailings 

1 

and grinding (minus 


1 50 mesh) 


~1 
Fine tailings 




1 
Scavenger tabling 






1 
Concentrate 




Coarse tailings 




"1 

Fine tailings 




~^ 






Acid scrubbing 




Cone 


1 

entrate 

i 

: separation 




1 
Decant tailings 


Magneti 






Magnet 


1 

c fractions 




1 

Nonmagneti 


cs 



Figure 14.— Flow diagram of columbium beneficiation proce- 
dure. 



Tables 8 and 9 show the results of beneficiation of 
samples A and B. A calculated composite concentrate from 
sample A contained 57 pet of the columbium at a grade of 
0.86 pet Cb. A calculated composite concentrate from 
sample B contained 53 pet of the columbium at a grade of 



Table 8. — Gravity and magnetic concentration of sample A 



17 



„ , Analysis, pel 

Product wt pet 

Cb Zr 

Rougher and seavenger concentrates: 
Magnetics: 

With hand magnet' 0.4 0.06 0.03 

At 700 G 1 .09 .04 

At 1,500 G 3 .42 .09 

At 2,200 G .3 1.06 .13 

At 4,000 G 1.6 1.06 .17 

At6,200G 1.0 - 1.01 .33 

At 7,600 G 4 1.10 .27 

At 8,700 G 8 1.12 .67 

At 9,500 G 4 1.15 .26 

Nonmagneties at 9,500 G 1.9 42 1 39 

Weight loss from acid scrubbing 2.9 NA NA 

Subtotal 

Rougher table fine tailings 

Scavenger table coarse tailings 

Seavenger table fine tailings 

Composite or total 100.0 .10 .05 

Calculated composite concentrate^ 6.7 .86 .60 

NA Not analyzed. NAp Not applicable. 
'Additional analysis: 63.6 pet Fe, 

^Mathematical combination of magnetics at 1.500. 2,200, 4,000. 6.200, 7,600 
9,500 G. 



Distribution, pet 



Sr 



Cb 



Zr 



Sr 



0.03 


0.3 


0.2 


<0.1 


.09 


.1 


-;.1 


<.1 


.15 


1.2 


.6 


.1 


.25 


3.3 


.7 


.1 


.47 


17.3 


5.2 


1.3 


.73 


10.4 


6.3 


1.2 


.64 


4.3 


2.0 


.4 


.98 


8.7 


9,8 


1.3 


.70 


4.2 


1.8 


.4 


1 99 


7.8 


48.1 


6.1 


NA 


NAp 


NAp 


NAp 



10.1 


NA 


NA 


NA 


57.6 


74.7 


10.9 


47.5 


.04 


.02 


.39 


18.7 


17.5 


30.2 


27.3 


.06 


.01 


.97 


162 


50 


43.3 


15.1 


.05 


.01 


.63 


7.5 


2.8 


15.6 



.61 
1.00 



100.0 
57.2 



100.0 
74.5 



100.0 
10.9 



8.700. and 9.500 G. and nonmagneties at 



Table 9. — Gravity and magnetic concentration of sample B 



□ , . . . Analysis, pet 
Product wt pet 1 -— 

Cb Zr 

Rougher and scavenger concentrates: 
Magnetics: 

With hand magnet' 0.3 02 -0 01 

At 700 G 1 .11 ,02 

At 1.500 G .2 .65 04 

At 2,200 G 6 1.03 .05 

At 4,000 G .7 1.16 07 

At 6,200 G 1.8 1.07 .09 

At 7,600 G 6 1.07 08 

At 8,700 G .9 1,06 11 

At 9,500 G 5 1.05 .11 

Nonmagneties at 9,500 G 1.5 .65 .34 

Weight loss from acid scrubbing 2.3 NA NA 

Subtotal 

Rougher table fine tailings 

Scavenger table coarse tailings 32.9 

Scavenger table fine tailings 

Composite or total 100.0 12 .03 

Calculated composite concentrate^ 6.8 .97 .14 

NA Not analyzed. NAp Not applicable. 
'Additional analysis: 62,0 pet Fe. 

^Mathematical" combination of magnetics at 1,500, 2.200. 4,000 6 200 7 600 
9,500 G. 



Distribution, pet 



Sr 



Cb 



.17 
.22 



100.0 
53.3 



Zr 



100.0 
32.9 



Sr 



0.01 


0.1 


^-0.1 


^0.1 


.02 


.2 


■..1 


■-.1 


.04 


1.2 


.3 


.1 


.09 


4.7 


1.0 


.3 


.11 


7.0 


1.7 


.5 


.15 


15.8 


5.6 


1.6 


.15 


5.2 


1.7 


.5 


.20 


7.8 


3.5 


1.1 


.18 


3.9 


1.7 


.5 


.52 


7.7 


17.4 


4,5 


NA 


NAp 


NAp 


NAp 



9.5 


NA 


NA 


NA 


53.6 


32.9 


9.1 


45.1 


.05 


.02 


.11 


18,3 


31.4 


29.*4 


32.9 


.08 


.02 


,24 


21.1 


22.9 


46.7 


12.5 


.07 


03 


.20 


7.0 


12.8 


14.8 



100.0 
9.1 



8.700. and 9.500 G, and nonmagneties at 



0.97 pet Cb. In each case the grade could be improved to 
1.1 pet Cb with a sacrifice of 9 pet in recovery. 

The concentrates also contained zirconium and 
strontium. The calculated composite concentrate from 
sample A contained 74.5 pet of the zirconium and nearly 



11 pet of the strontium with grades of 0.60 pet and 1.00 
pet, respectively. The concentrate from sample B con- 
tained nearly 33 pet of the zirconium and 9 pet of the 
strontium with grades of 0.14 pet and 0.22 pet, respective- 
ly. 



18 



DISCUSSION 



ORIGIN OF THE REGOLITH 

The ferruginous regolith on upper Idaho Gulch is 
derived from chemical weathering of the underlying 
dolomitic marble. Most of the constituents of the regolith, 
including apatite, zircon, and a mixed assemblage of iron 
oxide minerals, are also found downdip in the less 
weathered marble. Columbium minerals and monazite 
have not been found in the marble; however, analyses 
show the marble contains trace amounts of columbium, 
cerium, and P2O5. 

The origin of the marble is not as clear. Beds of 
limestone, dolomite, or marble are unknown elsewhere 
within the extensive Mesozoic flysch belt (17). The marble 
and possibly associated metasedimentary wall rocks could 
be older than the flysch and correlative to a unit of 
Paleozoic-age limestone, dolomite, argillite, phyllite, 
metachert, and quartz-mica and chlorite schist that is 
exposed west of Tofty near the Yukon River {17). Near 
Tofty, this material could either occur as fault-bounded 
slivers intercalated within the flysch, or underlie the 
flysch and be exposed in an erosional window. Significant- 
ly, apatite, which is characteristic of the marble on upper 
Idaho Gulch, has not been identified in the Paleozoic-age 
carbonate rocks west of Tofty. 

Alternatively, the marble and regolith on upper Idaho 
Gulch may represent a carbonatite and its residual 
weathering product. Calcite, ankeritic dolomite, biotite, 
fluorapatite, monazite, xenotime, magnetite, pyrite, ana- 
tase, hematite, zircon, columbium-bearing rutile, ilmeno- 
rutile, columbite, and aeschynite are present in the 
regolith and/or marble. This mineralogy closely resembles 
that of the apatite-magnetite variety of carbonatite as 
described by Pecora <20). Similarly, the trace element 
composition of the marble and/or regolith closely resem- 
bles that of carbonatites (table 10). Particularly close 
agreement for level of concentration of trace elements 
exists for barium, titanium, and P2O5. 

Magnetite and P2O5 and to a lesser extent, co- 
lumbium and zirconium, are concentrated in the regolith 
to levels above those in the parent marble (table 10). This 
upgraded material is directly comparable to upgraded 
concentrations of magnetite, P2O5, columbium, and 
zirconium in residual soils overlying the Sukula carbona- 
tite complex in southeastern Uganda (21), in "apatite- 
francolite regolith" overlying the Sokli carbonatite com- 
plex in Finland (22), and elsewhere (23). 

The overall interpreted regional geologic setting and 
the rock assemblages found on upper Idaho Gulch are not 
overwhelmingly similar to those of classic carbonatite 
occurrences (20, 24). In particular, no alkalic igneous 
rocks or alkali-rich alteration halo have been identified in 



the Tofty area. However, it is possible that the marble 
intruded along the structurally complex northwestern 
margin of the flysch basin and that any associated alkalic 
rocks or alteration halo either remain hidden beneath the 
extensive silt cover or have not yet been exposed by 
erosion. Alternatively, poorly exposed and preserved 
occurrences of serpentinized rock in the vicinity of upper 
Idaho Gulch may represent metamorphosed mafic alkalic 
rocks. 

The grade and tonnage of the identified columbium 
resource on upper Idaho Gulch is considerably lower than 
that in exploitable columbium-bearing carbonatites 
worldwide. However, uneconomic columbium grades 
similar to or lower than those on upper Idaho Gulch have 
been identified in carbonatites elsewhere. Specifically, at 
Magnet Cove, AR, only 6 of 21 samples of the carbonatite 
exposure in Kinsey Quarry contained detectable co- 
lumbium with concentration ranging between 0.01 and 
0.07 pet (18). Additionally, it should be noted that the 
extent of the marble that underlies the regolith on upper 
Idaho Gulch is unknown, and that only three samples of 
marble have been analyzed. Therefore there is a possibil- 
ity for yet undiscovered, possibly higher grade columbium 
resources in the Tofty area. 

SOURCES OF PLACER MINERALS 

The bedrock source of the tin belt placer minerals is 
unknown. Wayland (8) outlines two hypotheses to explain 
possible origins. One suggests the northeast alignment of 
placer deposits reflects the trend of an ancient stream 
channel that has been reworked by younger streams. In 
this hypothesis, the placer minerals would have been 
derived from a source outside of the tin belt. The other 
hypothesis proposes that the placer constituents were 
derived from sources within the tin belt and that the 
placer deposits were formed from virtual in-place weath- 
ering. Wayland concludes that the second theory probably 
best explains the origin of the cassiterite, but that "the 
monazite, aeschynite, apatite, and zircon can be accounted 
for under either hypothesis" (8, p. 403). 

This investigation shows that a source for some of the 
placer minerals lies within the tin belt, northwest of the 
existing placer deposits. High concentrations of radioac- 
tive minerals and columbium in placer gravels on Idaho 
Gulch likely result from erosion of ferruginous regolith 
on upper Idaho Gulch. High concentration of radioactive 
minerals and columbium in tailings piles on Miller and 
Deep Creeks and the reported presence of apatite- and 
magnetite-bearing dolomite on Harter Gulch (8) likewise 
suggest additional lode sources in the headwaters of those 
creeks. 



Table 10. — Trace-element abundances and variations in reported (20) carbonatite deposits and marble 

and regolith on upper Idaho Gulch, percent 



Trace Reported . . . , , □ „„, .1,2 
element carbonatite ^^'^^^ "^9°"'^ 


e^/nt c^ZTl ^^arb,e- RegoNth^ 


Ce^ 02 - '' 06 -0 24 0-0 20 


Zr 0.001-0 02 0.02-0 065 -0.09 


Ba 05 -10.0 NA 5->6 


Ti 10 -3.0 NA 2 - 2.0 


Sr 50-2.0 NA - 40 

Cb 001- .5 025- 073 - 12 


PjOs 10 -6.0 132-2.74 .14-21.4 



NA Not analyzed 

'Only 3 samples collected (see table 6) 

^See tables 2 and 3 

'Includes all rare-earth elements. 



19 



SUMMARY AND CONCLUSIONS 



Two parallel N 60 E trending, northwest-dipping 
lenses of slightly radioactive iron-rich regolith were 
identified on upper Idaho Gulch in 1956 and investigated 
in 1984 by the Bureau of Mines. The regolith contains 
major amounts of magnetic and nonmagnetic iron oxide 
minerals, abundant apatite and zircon, moderate amounts 
of pyrite, monazite, and columbium-bearing rutile. The 
regolith also contains trace amounts of xenotime and the 
columbium minerals aeschynite, columbite, and ilmeno- 
rutile. Trace to major concentrations of barium, strontium, 
lanthanum, cerium, yttrium, silver, and titanium have 
also been identified. Each lens has a strike length of 
approximately 1,200 ft and persists for 200 to 250 ft 
downdip where unweathered magnetite-pyrite-apatite- 
zircon-bearing dolomitic marble has been encountered in 
drill core. 

High columbium and generally higher zirconium and 
P2O5 concentrations are restricted to a central, hematite- 
rich, red-brown portion of the regolith lenses. These 
mineralized zones have an average thickness of approx- 
imately 22 ft, probably decrease in thickness by 50 pet 150 
ft downdip, and have average columbium grades between 
0.04 pet and 0.07 pet. Given these dimensions and at a 
grade of 0.07 pet Cb, the regolith lenses on upper Idaho 
Gulch contain approximately 340,000 lb of columbium 



resources. Approximately 30,000 lb of this resource is 
indicated whereas 310,000 lb is inferred. Large additional 
columbium resources are probably present in the dolo- 
mitic marble. The regolith also contains inferred re- 
sources of approximately 340,000 lb of zirconium and 
12,250 st of P2O5. 

Calculated composite concentrates from two large 
samples of regolith contained 53 and 57 pet of the 
columbium at grades of 0.97 and 0.86 pet Cb, respectively. 
In each case the grade could be improved to 1.1 pet Cb 
with a sacrifice of 9 pet recovery. 

The unweathered source of the regolith, a dolomitic 
marble, could be of either igneous or sedimentary origin. 
Its mineralogy and trace-element geochemistry and the 
similarity of the regolith to descriptions of other co- 
lumbium-enriched regoliths suggest the marble is a 
carbonatite. However, the lack of associated alkalic 
igneous rocks or alkali-rich alteration halo and the 
stratiform nature of the regolith can be interpreted as 
evidence for sedimentary origin of the marble. 

The marble and regolith are a lode source for some of 
the minerals of the Tofty placer deposits. Similar bedrock 
geology or placer mineralogy suggests that additional lode 
sources may exist in the headwaters of Miller Gulch, Deep 
Creek, and Harter Gulch. 



REFERENCES 



1. Morgan, J. D. Strategic and Critical Materials. Pres. at 
AIME All-Institute Sess., Strategic and Critical Miner, and 
Foreign Policy, Las Vegas, NV, Feb. 27, 1980, 20 pp.; available 
from J. D. Warner, BuMines, Fairbanks, AK. 

2. Cunningham, L. D. Columbium. Ch. in Mineral Facts and 
Problems, 1985 Edition. BuMines B 675, 1985, pp. 185-196. 

3. Wahrhaftig, C. Physiographic Divisions of Alaska. U.S. 
Geol. Surv. Prof. Pap. 482, 1965, 52 pp. 

4. Eakin, H. M. A Geologic Reconnaissance of a Part of the 
Rampart Quadrangle, Alaska. U.S. Geol. Surv. Bull. 535, 1913, 
38 pp. 

5. Mining in the Hot Springs District. U.S. Geol. Surv. 

Bull. 622-G, 1915, pp. 239-245. 

6. Mertie, J. B., Jr. Mineral Deposits of the Rampart and Hot 
Springs Districts, Alaska. U.S. Geol. Surv. Bull. 844-D, 1934, pp. 
163-226. 

7. Thorne, R. L., and W. S. Wright. Sampling Methods and 
Results at the Sullivan Creek Tin Placer Deposits, Manley Hot 
Springs, Tofty, Alaska. BuMines RI 4346, 1948, 8 pp. 

8. Wayland, R. G. Tofty Tin Belt, Manley Hot Springs District, 
Alaska. U.S. Geol. Surv. Bull. 1058-1, 1961, pp. 363-414. 

9. Thomas, B. I. Tin-Bearing Placer Deposits Near Tofty, Hot 
Springs District, Central Alaska. BuMines RI 5373, 1957, 56 pp. 

10. Waters, A. E., Jr. Placer Concentrates of the Rampart and 
Hot Springs Districts. U.S. Geol. Surv. Bull. 844-D, 1934, p. 241. 

11. Moxham, R. M. Reconnaissance for Radioactive Deposits in 
the Manley Hot Springs-Rampart District, East-Central Alaska, 
1948. U.S. Geol. Surv. Circ. 317, 1954, 6 pp. 

12. Southworth, D. D. Columbium in the Gold- and Tin- 
Bearing Placer Deposits Near Tofty, Alaska. BuMines OFR 
174-84, 1984, 25 pp. 

13. Chapman, R. M., W. Yeend, W. P. Brosge, and H. N. Reiser. 
Reconnaissance Geologic Map of the Tanana Quadrangle, 
Alaska. U.S. Geol. Surv. Open File Rep. 82-734, 1982, 20 pp. 

14. Chapman, R. M., F. R. Weber, and B. Taber. Preliminary 



Geologic Map of the Livengood Quadrangle, Alaska. U.S. Geol. 
Surv. Open File Rep. 71-66 (483), 1971, 2 sheets. 

15. Foster, H. L., J. Laird, T. E. Keith, G. W. Gushing, and W. 
D. Menzie. Preliminary Geologic Map of the Circle Quadrangle, 
Alaska. U.S. Geol. Surv. Open File Rep., 83-170A, 1983, 32 pp. 

16. Jones, D. L., N. J. Silberling, R. M. Chapman, and P. 
Coney. New Ages of Radiolarian Chert From the Rampart 
District, East-Central Alaska. U.S. Geol. Surv. Circ. 868, 1984, 
pp. 39-73. 

17. Chapman, R. M. (U.S. Geological Survey). Private com- 
munication, 1985; available upon request from J. D. Warner, 
BuMines, Fairbanks, AK. 

18. Fryklund, V. C, Jr., R. S. Harner, and E. P. Kaiser. 
Niobium (Columbium) and Titanium at Magnet Cove and Potash 
Sulphur Springs, Arkansas. U.S. Geol. Surv. Bull. 1015-B, 1954, 
pp. 23-57. 

19. U.S. Bureau of Mines and the U.S. Geological Survey. 
Principles of a Resource/Reserve Classification for Minerals. U.S. 
Geol. Surv. Circ. 831, 1980, 5 pp. 

20. Pecora, W. T. Carbonatites: A Review. Geol. Soc. America 
Bull. v. 67, 1956, pp. 1537-1556. 

21. Reedman, J. H. Resources of Phosphate, Niobium, Iron, 
and Other Elements in Residual Soils Over the Sukulu 
Carbonatite Complex, Southeastern Uganda. Econ. Geol., v. 79, 
1984, pp. 716-724. 

22. Vartiainen, H., and H. Paarma. Geological Characteristics 
of the Sokli Carbonatite Complex, Finland. Econ. Geol., v. 74, 
1979, pp. 1296-1306. 

23. Deans, T. Economic Mineralogy of African Carbonatites. 
Ch. in Carbonatites, ed. by O. F. Tuttle and J. Gittens. Wiley, 
1966, pp. 385-416. 

24. Parker, R. L., and J. W. Adams. Niobium (Columbium) and 
Tantalum. Paper in United States Mineral Resources, ed. by D. 
A. Brobst and W. P. Pratt. U.S. Geol. Surv. Prof Pap. 820, 1973, 
pp. 443-454. 



20 



APPENDIX A.— MODIFIED 1956 DRILL CORE LOGS AND GEOLOGIC CROSS 
SECTIONS CONSTRUCTED FROM DRILL CORE DATA 

Tables A-1 through A-9 are logs of diamond drill holes D-1 through D-9. Geologic cross sections through drill holes 
D-1 through D-9 and trench T-8 are presented in figures A-1 through A-6. 

Table A-1. — Log of diamond drill hole 0-1, Idaho Gulch 



Bearing 

Inclination ... 
Collar elevation 



S 14 E 
45 
852 



Depth ft . . 

Size: NX. to 15.5 ft; BX, 15.5 to 119.5 ft; AX, 119.5 to 194.0 ft. 



194.0 



Interval, ft 



Recovery, ft 



Description 



0.0 to 9.8 
9.8 to 39 7 
39.7 to 56.6 
56.6 to 126.5 
126.5 to 132 2 

132.2 to 143.3 

143.3 to 162.8 
162.8 to 194.0 



0.70 

5.15 
.30 

2.45 


.35 
10.70 

6.85 



Muscovite-quartz schist, weathered with limonite on fractures. 

Dark quartz-muscovite schist with up to l-in-wide quartz veins and limonite on fractures. 

White quartzose phyllite with partings of muscovite phyllite and quartz veins. 

Black graphite-muscovite schist, minor pyrite and quartz veins. 

Black phyllite with limonite on fractures. 

Limonite (regolith) 

Gray to light-green calcareous quartz-chlorite-sericite phyllite. 

Dark-gray argillite and chloritic schist, limonite after pyrite and on fractures. 



Table A-2.— Log of diamond drill hole D-2, Idaho Gulch 

Bearing S 1 5- E Depth ft . . 179.4 

Inclination -68 30' Size; NX. to 14.5 ft; BX. 14 5 to 59.3 ft; AX, 59.3 to 179.4 ft. 

Collar elevation ft . . 52 

Interval, ft Recovery, ft Description 

0.0 to 3.0 0.00 Silt with fragments of phyllite. 

3.0 to 14.5 1.5 Muscovite-quartz schist, weathered with limonite on fractures. 

14.5 to 38 C) Dark quartz-muscovite schist with local quartz veinlets. 

38 to 105 16.88 White to gray quartzose muscovite phyllite grading downward to thinly laminated quartz 

and muscovite schist with minor pyrite and muscovite-graphite phyllite. 
105 to 179.4 21.34 Muscovite-graphite pyllite grades downward into graphite-muscovite schist, and then, to 

graphitic argillite, Pyrite disseminated throughout. 

'Included with recovery from 38- to 105-ft interval. 

Table A-3. — Log of diamond drill hole D-3, Idaho Gulch 

Inclination -90° Depth 278.0 

Collar elevation ft . . 835.2 Size: BX, to 18.9 ft; AX, 18.9 to 206.2 ft; EX, 206.2 to 278.0 ft. 

Interval, ft Recovery, ft Description 

0.0 to 9.0 0.0 Frozen silt. 

9.0 to 58.0 ,99 Gray phyllite with limonite on fractures. 

58.0 to 60.0 .98 Quartz with limonite after pyrite. 

60.0 to 190.7 8.80 Interlaminated dark-gray to black quartz and muscovite-graphite schists, thin bands of 

quartz, some with pyrite. 

190.7 to 192.0 .45 Calcareous chlorite-sericite schist with limonite after pyrite and calcite veinlets. 

192.0 to 193.3 VO Granular limonite (regolith). 

193.3 to 264.7 (^) Dolomitic marble, weathered, yellow color with abundant quartz and magnetite grains, 

limonite after pyrite, and veinlets of limonite, calcite-dolomite, and apatite. 
264.7 to 278.0 38.97 Quartz-chlorite-sericite schist with disseminated magnetite and pyrite 

'Rock type identified from coarse cuttings in sludge. 
^Included with 264.7- to 278.0-ft interval. 

Table A-4. — Log of diamond drill hole D-4, Idaho Gulch 



inclination -90° Size: NX, to 20.0 ft; BX, 20.0 to 50.4 ft; AX, 50.4 to 184,7 ft; EX, 184.7 

Collar elevation ft . . 81 1 to 259.8 ft 

Depth ft . . 259.8 

Interval, ft Recovery, ft Description 

0.0 to 5,0 '0.0 Frozen silt. 

5.0 to 40.0 '.0 Black phyllite. 

40.0 to 50.4 .25 Kaolinized phyllite. 

50.4 to 65.4 .43 Siliceous light gray phyllite with pyrite. 

65.4 to 75.4 .48 Decomposed Phyllite. 

75.4 to 1 35.4 10.71 Gray to black phyllite with thin quartz seams. 

135.4 to 174.1 15.86 Slightly calcareous quartz-chlorite-muscovite ± (talc-serpentine) phyllite with quartz along 

foliation. 
174.1 to 191 .0 ('^) Unweathered moderately coarsely crystalline dolomitic marble with disseminated 

magnetite, pyrite and pyrrhotite, and rare quartz veins, 
191 ,0 to 259.8 16.36 Limonite-stained calcareous dolomite marble with disseminated magnetite. More altered 

intervals include 225 to 228 ft and 232 to 245 ft, 

'Rock type identified from coarse cuttings in sludge. 
^Included with 191.0- to 259.8-ft intervals. 



21 

Table A-5.— Log of diamond drill hole D-5, Idaho Gulch 

Inclination -90 Size: NX. to 45.7 ft; BX. 45.7 to 75.4 ft; AX, 75.4 to 95.4 ft; EX, 95.4 to 

Collar elevation ft.. 801 155 1ft. 

Deptfi ft-- 155.1 

Interval, ft Recove ry, ft Description 

0.0 to 5.0 '0.0 Frozen silt, granular dolomite, and limonite. 

5 to 10,0 ■15 Phyllite, quartz, and granular limonite 

10 to 27.9 8,84 Weathered, granular rock with coarse dolomite grains in a fine limonitic matnx. Contains 

fragments of chloritic material, magnetite, limonite after pyrite, pyrite, limonite on 

fractures, and quartz veins. 
27.9 to 65.4 20.39 Coarse dolomitic marble with disseminated magnetite, pyrite, and trace pyrrhotite. fwlinor 

hematite after magnetite and local limonite on fractures. Chloritic at base. 

65.4 to 80.4 3.85 Gray calcareous phyllite 

80.4 to 155.1 101 Black phyllite with quartz veinlets. 

'Rock type identified from coarse cuttings in sludge. 

Table A-6.— Log of diamond drill hole D-6, Idaho Gulch 

Inclination -90" Depth ft., 134.6 

Collar elevation ft.. 827 Size: NX, to 5.0 ft; BX. 5.0 to 45.0 ft; AX, 45.0 to 134.6 ft. 

Interval, ft Recovery, ft Description 

0.0 to 5.0 0.0 Frozen silt and schist fragments, 

5,0 to 18,0 17 Frozen, fractured arid aliered muscovite-graphite phyllite, 

18,0 to 25,0 .78 Fractured and weathered muscovite phyllite, minor quartz veins and limonite. 

25,0 to 61 ,0 .30 Frozen granular limonite, some magnetite (regolith). 

61 .0 to 70 (') Weathered and fractured limonitic marble, locally chlorite- and sericite-rich with dissem- 

inated magnetite, hematite, and limonite after pyrite and veinlets of limonite and caicite. 

70.0 to 74.4 (') Porous limonite with caicite veinlets. 

74.4 to 75.0 (') Kaolinitic schist, 

75.0 to 95.4 24.9 Interfoliated muscovite = chlorite i sericite schists with minor limonite after pyrite and 

on fractures, 

95.4 to 1 10.4 5.68 Chlorite-quartz-calcite schist. 

110.4 to 134.6 6.00 Interfoliated dolomitic limestone and pyritic graphite schist. 

'Included with 75.0- to 95.4-ft interval. 

Table A-7. — Log of diamond drill hole D-7, Idaho Gulch 



Inclination -90" Depth ft . . 

Collar elevation ft . , 832 Size: BX, to 44.3 ft. 

Interval, ft Recovery, ft Description 

0.0 to 14.3 (') Dark, goethite-limonite hematite-bearing regolith. nonmagnetic, 

14.3 to 19.3 3.71 Orange earthy limonitic regolith with fragments of chloritic phyllite, 

19.3 to 19.8 ,5 Kaolinitic clay with a few fragments of metallic goethite, 

19.8 to 43.3 16.55 Nonfoliated. chlonte-sericite-quartz phyllite with segregations of chlorite-serpentine. 

'Included with 14.3- to 19.3-ft interval. 



44.3 



Table A-8. — Log of diamond drill hole D-8, Idaho Gulch 



Inclination -90 Depth ft 

Collar elevation ft , , 836 Size: NX, to 5,0 ft: BX, 5,0 to 50,3 ft 



50,3 



Interval, ft 


Recovery, ft 


Description 


0.0 to 5.0 


(') 


Earthy, limonitic magnetic regolith. 
Nonmagnetic limonitic regolith 

Chlorite-talc-sericite-(serpentine) schist, locally calcareous and altered to kaolinite and 
limonite 


5.0 to 13.8 . 


2 64 


13.8 to 50.3 . 


4 95 







'Included with 5.0- to 13.8-0 interval. 



Table A-9.— Log of diamond drill hole D-9, Idaho Gulch 



Inclination -90° Depth ft . 

Collar elevation ft 851 Size: BX, to 30.3 ft; AX, 30.3 to 143.9 ft 

Interval, ft Recovery, ft Description 

0.0 to 45.3 3.08 Dark-gray to blue-colored weathered and fractured phyllite; locally limonitic. 

45.3 to 50.3 1 .85 Chloritic schist. 

50.3 to 74.3 2,60 Dark-gray to blue-colored decomposed phyllite with iron-stained quartz, 

74.3 to 89,4 1.63 Frozen granular limonite (regolith), 

89.4 to 93,7 1.85 Dark-gray calcareous schist. 

93.7 to 109.6 .70 Chlorite schist, slightly calcareous, with thin quartz seams that contain pyrite. 

109.6 to 110.4 '.0 Talc schist 

110.4 to 112.8 '.0 Granular limonite. 

112.8 to 143.9 5^0 Gray, slightly calcareous schist. 

'Rock type identified from coarse cuttings in sludge. 



143.9 



22 



Eliv,ft 
690 



800 



750 



700 



D-l D-2 




Depth 194 ft 



Dapth 179.4 ft 

Figure A-1. — Geologic section through drill holes D-1 and 
D-2 and trench T-8. 




NW 



Dtpfh 44 3 ft 

Figure A-3. — Geologic section through drill hole D-7 and 
trench T-8. 



SE 



Eltv.ft 
800 




Figure A-2. — Geologic section through drill holes D-3 and 
D-6 and trench T-8. 



i^ 









LEGEND 
Quartz - muscovite phyllite end scttist 
Muscovitic quartzlte end schist 
Graphite -muscovite phyllite, dotted where siliceous 



x'\''>''^ Chlorite-sericitei quartz ttalc± serpentine phyllite and schist 



Nonfoliated chloritic rock 
ra Regoiith 

^3 Oolomitic marble 
y Geologic contoct, dashed where approximate, dotted where inferred 



60 

J_ 



120 

_J 



Scale, feet 



23 





Depth 259.8 ft 



Figure A-4. — Geologic section tlirough drill hole D-8 and Figure A-6. — Geologic section through drill holes D-4 and 

trench T-8. D-5 and trench T-6. 




Depth 143.9 ft 

Figure A-5.— Geologic section through drill hole D-9 and 
trench T-8. 



i^ 



:i^ 



^ 






LEGEND 
Quartz -muscovite phyllite and schist 
Muscovitic quartzite and schist 
Graphite -muscovite phyllite, dotted where si liceous 
Chlorite-sericite± quartz ttalc± serpentine phyllite and schist 

Nonfoliafed chloritic rock 
Regollth 



^3 Dolomitic morble 

./ Geologic contocf, dashed where approximate, dotted where inferred 



60 
I 



Scale, feet 



120 

_J 



24 



APPENDIX B.— TEST PROCEDURE FOR CHARACTERIZATION OF TOFTY REGOLITH 

CONCENTRATES 5, 9, 15, AND 30 



Planned concentrate samples were acid leached in a 
1:1 HCl solution to remove excess iron oxide. The material 
was then screened at 20 mesh. The plus 20-mesh fraction 
was optically, radiometrically, and spectroscopically ex- 
amined and was found to contain no properties character- 
istic of the suspected columbium-bearing minerals. The 
remaining minus 20-mesh fraction of each sample was run 
through a laboratory-model isodynamic magnetic separ- 
ator at 0-, 0.1-, 0.2-, 0.3-, 0.4-, 0.5-, 0.6-, 1.0-, and 1.7-A 
settings to isolate minerals of similar magnetic suscepti- 
bilities. These fractions were examined optically, 
radiometrically, and spectroscopically to determine possi- 
ble concentrations of columbium-bearing minerals. The 
fractions determined to contain the highest concentration 
of columbium were prepared in polished grain mounts for 
scanning electron microscope (SEM) and microprobe 
studies. Aeschynite was positively identified by SEM 
methods and found to be well concentrated in the 0.7-A 
magnetic fraction. Columbite was also identified and 



found concentrated in the 0.5-A magnetic fraction. 
Columbium-bearing rutile (possibly altered in part to 
ilmenorutile) was also concentrated in the 0.5-A fraction. 
Table B-1 summarizes the results of the analyses. 



Table B-1. — Mineralogical analyses of magnetic^ fractions of 

samples representative of the regolith concentrates selected 

for SEM studies, weight percent 



Magnetic fraction A 0.3 0.4 0.5 0.7 

Magnetite 35 ND ND ND 

Goethite 35 60 ND ND 

Miscellaneous silicates 20 25 15 10 

Columbite 6 6 20 ND 

Monazite 4 4 ND ND 

Aeschynite ND 2 5 70 

Rutile ND ND ND 10 

Zircon ND ND 60 10 

Other ND ND ND ND 

ND Not detected. 

'Separated on a laboratory-model isodynamic magnetic separator. 



1.0 



ND 
ND 
25 
ND 
ND 
45 
10 
15 
5 



25 



APPENDIX C— RESULTS OF EMISSION SPECTROGRAPHIC ANALYSES^ 

REGOLITH SAMPLES 



OF 



Sample 11 12 13 16 17 18 19 20 22 23 24 25 26 

CONCENTRATION, ppm 

Ag <70 <To <100 60 ioO <80 <40 <60 <400 <400 <100 < 300 --300 

As <200 1,000 900 <200 <200 <500 <400 <100 <1,000 <800 <90 <700 800 

Au <20 <40 <40 <20 <20 <50 <30 <20 <400 <400 <20 <30 <-50 

B <60 <100 <100 <40 <40 <100 <80 <30 <100 <100 <200 <100 <100 

Be 6 7 4 4 5 <3 <2 4 4 <3 4 5 5 

Bi <100 <100 <500 <2,000 <1.000 <100 <400 <200 <500 <100 <100 <6,000 <2,000 

Cb <400 600 200 <200 <300 <100 400 <100 300 400 600 <100 700 

Cd <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 

Co 50 100 50 60 80 200 100 <30 200 200 200 100 100 

Cr 100 700 200 1 ,000 400 800 500 70 300 400 1 ,000 2,000 600 

Cu 30 10 6 10 30 20 20 30 10 <6 9 <6 40 

Ga 20 30 20 <9 30 60 30 20 20 20 40 <2 20 

La <300 1,000 <300 <100 <100 1,000 1,000 <100 <100 <200 <200 <100 800 

Li <30 <20 <20 <20 <30 <30 <20 <20 <20 <20 <20 <;20 <20 

Mo <10 <10 <10 <10 <10 <10 <10 <1 <1 <1 <1 <1 <1 

Ni 200 700 600 1.000 400 900 800 100 <400 500 2,000 3,000 800 

Pb <50 100 <40 <60 <50 90 <20 <40 <20 <20 <50 <20 <20 

Pd <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 

Pt <40 <100 <80 <70 <50 <100 <100 <40 <100 <100 <200 <200 <100 

Sb <2,000 <2,000 <2,000 < 1,000 <2,000 < 1.000 < 1,000 <2.000 <3.000 <3,000 <2,000 <3,000 <3.000 

Sc <4 10 <4 <4 <5 10 <8 <4 <8 <8 <4 <4 <7 

Sn <200 <200 400 <200 <200 <200 <80 <200 <800 <70 <300 <200 <100 

Sr 100 4,000 1,000 3 10 1,000 700 300 300 200 40 30 1,000 

Ta <200 <200 <200 <200 <200 <200 <200 <200 <200 <200 <200 <200 <300 

."e <500 <400 <500 <400 <400 <400 <400 <400 <400 <400 <700 <400 <600 

Ti 5,000 10,000 5,000 3,000 7,000 7,000 5,000 4,000 9,000 10,000 4.000 2,000 6,000 

V 300 500 500 200 400 800 500 400 500 600 600 200 500 

Y <9 <10 <9 <9 <.9 <-9 <9 <.9 <9 <,9 <9 <9 <9 

Zn 100 90 40 100 100 <10 <4 -^20 <10 <10 <50 <40 60 

Zr 100 1.000 300 <30 60 400 200 100 2,000 1,000 100 <30 500 

CONCENTRATION, pet 

aI >5 >3 Oi >5 >6 >3 ] >6 ol i OS 09 >2 

Ba .6 >6 .8 07 .2 7 .5 1 .1 .08 .2 .1 .5 

Ca <.5 3 1 .4 .7 3 <.6 <.4 <.6 <.7 <.3 <.4 4 

Fe 10 10 10 8 9 10 10 10 >10 >10 >10 10 10 

K 10 579 10 747697 10 7 

Mg .4 .3 .3 1 1 .9 .4 .4 <.05 <.01 .2 .2 .2 

Mn >4 >5 >4 >2 >2 >6 >5 >4 >10 >10 >3 >9 >10 

Na <.3 <.3 <.3 <.3 <.3 <.3 <.3 <.3 <.3 <.3 <.3 <.3 <.3 

P <1 3 <2 <.7 <.7 <.7 <1 <.8 <.7 <.7 <.9 <1 2 

SI >10 5 >10 >10 >10 >10 >10 >10 >10 >10 >10 >10 >10 

'Analyses by Bureaus Reno Research Center, Reno, NV 



26 



RESULTS OF EMISSION SPECTROGRAPHIC ANALYSES' OF REGOLITH SAMPLES— Continued 



Sample 27 28 32 33 

Ag <300 <30 <80 <300 

As <800 <100 <200 <800 

Au <40 <20 <20 <40 

B <90 <50 <50 <100 

Be 1 4 8 <3 

Bi <200 <600 <100 <2,000 

Cb 300 <200 <300 <200 

Cd <5 <5 <5 -5 

Co 100 <20 200 90 

Cr 400 100 6.000 600 

Cu 6 100 30 20 

Ga 30 <10 20 <9 

La 300 <100 <100 <100 

Li <20 <20 <20 <20 

Mo <1 <1 <1 <1 

Ni 400 100 3,000 1,000 

Pb <20 <20 <60 <20 

Pd <1 <1 <1 -1 

Pt <100 <6 <300 <100 

Sb <2,000 <600 <3,000 <3,000 

So <4 <4 <9 <4 

Sn <20 <80 <300 <200 

Sr 400 20 100 80 

Ta <200 <200 <300 <200 

Te <400 <400 1 ,000 -^400 

Ti 7,000 10.000 3,000 10,000 

V 500 400 400 500 

Y <9 <9 <9 -9 

Zn <1 <30 200 40 

Zr 2,000 40 90 200 

AJ i >6 ^ ,3 

Ba .3 .1 .3 .4 

Ca <.6 1 <.4 <.8 

Fe 10 7 10 10 

K 6 10 8 9 

Mg .2 1 .4 .3 

Mn >10 .3 >4 >8 

Na <.3 2 <.3 <.3 

P <2 <.7 <2 <1 

Si >10 >10 >10 >10 

'Analyses by Bureau's Reno Research Center, Reno, NV. 



34 



35 



36 



37 



38 



39 



40 



41 



CONCENTRATION, ppm 



<70 
<800 

<50 

<100 

<3 

<200 
800 
•-5 
100 
200 

40 

20 

300 

<20 

<1 

800 

<20 

<1 

<100 

<' 3.000 

■4 
<200 

50 
-200 
-400 

10.000 

600 

-9 

- 60 

400 



5 

90 

■100 

- 300 

5 

■ 200 
1,000 

5 
400 
300 

100 

70 

300 

• 20 
■ 1 

2.000 
60 
- 1 

■ 300 
3.000 

20 
800 

70 
200 
900 

20,000 

1.000 

9 

• 20 
4,000 



■ 40 

■ 90 
' 50 

-100 
4 

■ 100 
200 

• 5 
60 

200 

20 

'-10 

<100 

<20 

•1 

400 

'30 

- 1 

'70 

■3,000 

■-4 

■ 200 
1,000 

■ 300 

■ 600 

10,000 
600 

• 9 

■ 40 
90 



- 70 

'90 

'20 

'200 

8 

■ 700 

• 70 

■ 5 
80 

500 

50 

'JO 

■;100 

'20 

■-1 

600 

<70 

■:1 

'90 

'.4.000 

■A 
600 
2.000 
100 
900 

10,000 
800 

■ 9 

• 20 
100 



• 40 
100 

■ 20 

100 

7 

100 

■ 100 

• 5 

' 10 

50 

40 

■-8 

'-100 

';20 

■1 

200 
30 
-.1 

■ 20 
■-600 

■ 4 
100 
8 
200 
400 

6,000 

200 

9 

80 

'30 



'50 

-^100 

20 

• 70 

6 

'100 

';100 

' 5 

' 10 

200 

50 

<2 

'-100 

'20 

<1 

400 

• 20 
--1 

■30 
'^600 

-.4 

';100 

60 

-^200 

400 

6,000 

100 

'9 

80 

30 



200 

; 1 ,000 

<20 

100 

4 

-^100 

■'100 

<5 

100 

200 

100 
60 

300 
80 
<1 

200 

100 

•-1 

■;20 

';700 

<5 
<300 

100 
<200 
<400 

7,000 

700 

•-10 

--2 

200 



100 
<90 
<20 

100 
9 

<100 

<200 

<5 

70 

100 

100 

40 

<300 

70 

<1 

400 

--80 

<1 

<6 

;2,000 

<5 

<300 

100 

<200 

'-900 

6.000 
400 
-9 
200 
100 



CONCENTRATION, pet 



0.8 
.1 
-.2 
-10 
9 

.2 
:-5 

<.3 
<1 
'10 



10 
4 



'7 



<2 

-10 



0.7 
.2 
•10 
-10 

7 

.5 
-5 
'..3 
6 
3 



-10 
-10 
<1 



.2 
.9 
8 
-10 

1 

.7 
<.3 
<? 
-10 



2 

9 

>10 

1 

>2 
<.3 
<.7 

-10 



>7 
1 

<.1 
9 
>10 

.4 
>3 
<.3 
<.7 
>10 



>6 



.6 
.7 
>10 
10 

.4 
>2 
<.3 
<.7 
>10 



27 



APPENDIX D.- 



-RESULTS OF MAGNETIC,' RADIOMETRIC,' AND SOIL SAMPLE' 

SURVEYS 



station 


Magnetic 
intensity, 
gammas 


Radioactivity, 
cps 


Cb, 
ppm 


P3O5. 
pet 


Zn. 
ppm 


Station 


Magnetic 
intensity, 
gammas 


Radioactivity, 
cps 


Cb. 
ppm 


P2O5. 
pet 


Zn. 
ppm 






LINE 9,600 NE 










LINE 10,000 NE 






9,500 SE . 


572 


73 


NS 


NS 


NS 


9,500 SE 


518 


80 


NS 


NS 


NS 


9,525 SE 


524 


72 


NS 


NS 


NS 


9.525 SE 


541 


87 


NS 


NS 


NS 


9,550 SE 


507 


73 


NS 


NS 


NS 


9.550 SE 


536 


97 


NS 


NS 


NS 


9,575 SE 


521 


72 


NS 


NS 


NS 


9.575 SE 


536 


106 


NS 


NS 


NS 


9,600 SE 


522 


68 


NS 


NS 


NS 


9.600 SE . 


569 


93 


NS 


NS 


NS 


9,625 SE . 


520 


76 


NS 


NS 


NS 


9.625 SE 


580 


83 


NS 


NS 


NS 


9,650 SE . 


520 


76 


NS 


NS 


NS 


9.650 SE . 


597 


85 


NS 


NS 


NS 


9,675 SE 


514 


76 


NS 


NS 


NS 


9.675 SE 


605 


79 


NS 


NS 


NS 


9,700 SE 


510 


83 


NS 


NS 


NS 


9.700 SE 


653 


86 


NS 


NS 


NS 


9,725 SE 


515 


74 


NS 


NS 


NS 


9.725 SE 


674 


86 


NS 


NS 


NS 


9,750 SE 


531 


73 


NS 


NS 


NS 


9.750 SE 


692 


86 


NS 


NS 


NS 


9.775 SE 


526 


72 


NS 


NS 


NS 


9.775 SE 


702 


95 


NS 


NS 


NS 


9,800 SE 


523 


67 


NS 


NS 


NS 


9.800 SE 


689 


110 


NS 


NS 


NS 


9,825 SE 


520 


66 


NS 


NS 


NS 


9.825 SE 


658 


93 


NS 


NS 


NS 


9,850 SE 


520 


66 


NS 


NS 


NS 


9.850 SE 


602 


113 


NS 


NS 


NS 


9,875 SE 


508 


70 


NS 


NS 


NS 


9.875 SE 


524 


102 


NS 


NS 


NS 


9,900 SE 


504 


70 


NS 


NS 


NS 


9.900 SE 


586 


114 


NS 


NS 


NS 


9,925 SE 


465 


78 


NS 


NS 


NS 


9.925 SE 


537 


103 


NS 


NS 


NS 


9,950 SE 


514 


71 


NS 


NS 


NS 


9.950 SE . 


536 


87 


NS 


NS 


NS 


9,975 SE 


515 


76 


NS 


NS 


NS 


9.975 SE 


524 


94 


NS 


NS 


NS 


10,000 SE 


530 


71 NS 
LINE 9.800 NE 


NS 


NS 


10.000 SE 


444 


96 


NS 


NS 


NS 








LINE 10,200 NE 






9,500 SE 


526 


75 


NS 


NS 


NS 


9.500 SE 


602 


91 


^;50 


014 


170 


9,525 SE 


522 


70 


NS 


NS 


NS 


9.525 SE 


600 


90 


<50 


.12 


190 


9,550 SE 


526 


72 


NS 


NS 


NS 


9.550 SE . 


595 


89 


<50 


.18 


210 


9,575 SE 


522 


72 


NS 


NS 


NS 


9.575 SE 


607 


87 


<50 


.16 


200 


9,600 SE 


530 


71 


NS 


NS 


NS 


9.600 SE 


620 


88 


<50 


.15 


180 


9,625 SE 


528 


84 


NS 


NS 


NS 


9.625 SE 


630 


95 


<50 


.13 


190 


9,650 SE 


530 


72 


NS 


NS 


NS 


9.650 SE . 


641 


96 


<50 


.12 


190 


9.675 SE 


545 


74 


NS 


NS 


NS 


9.675 SE 


641 


88 


<50 


.12 


180 


9,700 SE 


521 


70 


NS 


NS 


NS 


9.700 SE 


661 


95 


<50 


.10 


200 


9,725 SE 


530 


75 


NS 


NS 


NS 


9.725 SE 


672 


90 


<50 


10 


180 


9,750 SE 


535 


75 


NS 


NS 


NS 


9.750 SE 


661 


89 


NS 


NS 


NS 


9,775 SE 


529 


72 


NS 


NS 


NS 


9.775 SE 


643 


85 


■ 50 


.10 


180 


9,800 SE 


539 


72 


NS 


NS 


NS 


9.800 SE 


627 


88 


-50 


.12 


200 


9,825 SE 


523 


78 


NS 


NS 


NS 


9.825 SE . 


616 


93 


<50 


.11 


190 


9,850 SE 


527 


77 


NS 


NS 


NS 


9.850 SE 


610 


88 


<50 


.14 


180 


9.875 SE 


540 


78 


NS 


NS 


NS 


9.875 SE 


583 


94 


<50 


.36 


210 


9,900 SE 


524 


82 


NS 


NS 


NS 


9,900 SE 


557 


93 


<50 


.10 


170 


9,925 SE 


520 


87 


NS 


NS 


NS 


9,925 SE 


537 


111 


<50 


.29 


220 


9,950 SE 


520 


88 


NS 


NS 


NS 


9,950 SE . 


553 


109 


<50 


.11 


170 


9,975 SE 


524 


81 


NS 


NS 


NS 


9,975 SE 


523 


102 


<50 


.13 


180 


10.000 SE 


526 


83 NS 
LINE 10.000 NE 


NS 


NS 


10.000 SE 


508 


83 


• 50 


.17 


190 








LINE 10,300 NE 






9,500 SE 


566 


86 


<50 


0.35 


270 


9.500 SE 


632 


96 


NS 


NS 


NS 


9,525 SE 


559 


87 


<50 


.16 


190 


9,525 SE 


611 


101 


NS 


NS 


NS 


9,550 SE 


536 


84 


<50 


.18 


230 


9.550 SE . 


622 


102 


NS 


NS 


NS 


9,575 SE 


531 


81 


<50 


.13 


200 


9.575 SE 


630 


108 


NS 


NS 


NS 


9,600 SE 


562 


88 


<50 


.23 


180 


9.600 SE 


685 


116 


NS 


NS 


NS 


9,625 SE 


565 


92 


<50 


.16 


190 


9.625 SE 


694 


124 


NS 


NS 


NS 


9,650 SE 


447 


107 


<50 


.23 


190 


9.650 SE 


868 


115 


NS 


NS 


NS 


9.675 SE 


578 


106 


<50 


.16 


200 


9.675 SE 


636 


117 


NS 


NS 


NS 


9,700 SE 


685 


100 


<50 


.12 


170 


9.700 SE 


576 


86 


NS 


NS 


NS 


9,725 SE 


605 


91 


<50 


.16 


190 


9.725 SE 


586 


99 


NS 


NS 


NS 


9.750 SE 


648 


89 


<50 


.17 


190 


9.750 SE 


569 


96 


NS 


NS 


NS 


9,775 SE 


895 


87 


<50 


.20 


200 


9.775 SE 


545 


114 


NS 


NS 


NS 


9,800 SE 


645 


89 


<50 


.11 


190 


9.800 SE 


544 


190 


NS 


NS 


NS 


9,825 SE 


538 


91 


<50 


.26 


210 


9,825 SE 


626 


204 


NS 


NS 


NS 


9.850 SE 


512 


89 


<50 


.12 


170 


9,850 SE 


816 


214 


NS 


NS 


NS 


9.875 SE 


494 


92 


<50 


.14 


200 


9,875 SE 


527 


220 


NS 


NS 


NS 


9,900 SE 


519 


97 


<50 


.12 


190 


9.900 SE 


518 


147 


NS 


NS 


NS 


9,925 SE 


525 


99 


<50 


.20 


220 


9,925 SE 


519 


134 


NS 


NS 


NS 


9,950 SE 


546 


102 


<50 


.16 


200 


9,950 SE 


511 


110 


NS 


NS 


NS 


9,975 SE 


551 


97 


<50 


.14 


200 


9,975 SE 


489 


93 


NS 


NS 


NS 


10,000 SE 


540 


86 


<50 


.15 


220 


10,000 SE 


501 


92 


NS 


NS 


NS 



NS No sample, NR No reading. 

'Total-field magnetic intensity, all readings have a base of 56,000 gammas. 

^otal-count gamma-ray radiation. 

^Soil sample analyses by XRF by Bureau's Reno Research Center, Reno, NV. 



28 



RESULTS OF MAGNETIC,' RADIOMETRIC,^ AND SOIL SAMPLE^ SURVEYS— Continued 



Station 


Magnetic 
intensity. 


Radioactivity. 


Cb, 


P2O5, 


2n, 


Station 


Magnetic 
intensity, 


Radioactivity, 


Cb. 


P2O5, 


Zn, 




gammas 


ops 


ppm 


pet 


ppm 




gammas 


cps 


ppm 


pet 


ppm 






LINE 10,400 NE 










LINE 10,700 NE 






9,500 SE 


580 


86 


<50 


0.19 


180 


9,500 SE 


540 


73 


NS 


NS 


NS 


9,525 SE 


571 


88 


<50 




16 


190 


9,525 SE 


537 


75 


NS 


NS 


NS 


9,550 SE . 


581 


92 


<50 




13 


180 


9,550 SE 


527 


78 


NS 


NS 


NS 


9,575 SE 


576 


92 


<50 




13 


190 


9,575 SE 


521 


73 


NS 


NS 


NS 


9,600 SE 


645 


96 


<50 




13 


190 


9,600 SE 


508 


74 


NS 


NS 


NS 


9,625 SE . 


738 


113 


<50 




77 


210 


9,625 SE . 


507 


70 


NS 


NS 


NS 


9,650 SE . 


1081 


109 


<50 




32 


220 


9,650 SE . 


498 


81 


NS 


NS 


NS 


9,675 SE . 


887 


174 


NS 


NS 


NS 


9,675 SE . 


545 


79 


NS 


NS 


NS 


9,700 SE . 


576 


149 


250 


5.40 


460 


9,700 SE 


548 


78 


NS 


NS 


NS 


9,725 SE 


545 


112 


<50 


.29 


180 


9.725 SE 


535 


73 


NS 


NS 


NS 


9,750 SE 


397 


105 


<50 


.28 


230 


9,750 SE 


543 


81 


NS 


NS 


NS 


9.775 SE 


504 


98 


<50 


.17 


170 


9,775 SE 


576 


86 


NS 


NS 


NS 


9,800 SE 


548 


98 


<50 


.20 


200 


9,800 SE 


694 


84 


NS 


NS 


NS 


9,825 SE . 


560 


106 


<50 


.13 


170 


9,825 SE . 


900 


63 


NS 


NS 


NS 


9,850 SE 


582 


133 


<50 


.26 


210 


9.850 SE 


951 


71 


NS 


NS 


NS 


9,875 SE 


602 


167 


<50 


56 


330 


9,875 SE 


712 


62 


NS 


NS 


NS 


9,900 SE 


560 


250 


180 


2.60 


1160 


9,900 SE 


548 


60 


NS 


NS 


NS 


9.925 SE 


507 


179 


<50 


,52 


280 


9,925 SE 


521 


63 


NS 


NS 


NS 


9,950 SE 


510 


189 


70 


,89 


320 


9,950 SE 


519 


63 


NS 


NS 


NS 


9,975 SE . 


511 


124 


<50 


.31 


290 


9,975 SE 


530 


63 


NS 


NS 


NS 


10,000 SE 


532 


100 <50 
LINE 10,500 NE 


.20 


200 


10,000 SE 


507 


61 


NS 


NS 


NS 








LINE 10,800 NE 






9,500 SE 


582 


94 


NS 


NS 


NS 


9,500 SE 


567 


78 


NS 


NS 


NS 


9.525 SE 


551 


91 


NS 


NS 


NS 


9.525 SE , 


568 


81 


NS 


NS 


NS 


9.550 SE 


539 


86 


NS 


NS 


NS 


9.550 SE 


592 


79 


NS 


NS 


NS 


9.575 SE 


636 


81 


NS 


NS 


NS 


9,575 SE 


633 


75 


NS 


NS 


NS 


9,600 SE 


624 


87 


NS 


NS 


NS 


9,600 SE 


662 


73 


NS 


NS 


NS 


9.625 SE 


659 


103 


NS 


NS 


NS 


9,625 SE 


600 


82 


NS 


NS 


NS 


9.650 SE . 


677 


108 


NS 


NS 


NS 


9,650 SE . 


557 


104 


NS 


NS 


NS 


9,675 SE . 


608 


159 


NS 


NS 


NS 


9,675 SE . 


545 


101 


NS 


NS 


NS 


9.700 SE . 


587 


112 


NS 


NS 


NS 


9.700 SE , 


544 


88 


NS 


NS 


NS 


9,725 SE . 


586 


107 


NS 


NS 


NS 


9,725 SE . 


532 


65 


NS 


NS 


NS 


9,750 SE 


595 


90 


NS 


NS 


NS 


9.750 SE 


564 


62 


NS 


NS 


NS 


9,775 SE . 


594 


87 


NS 


NS 


NS 


9.775 SE . 


594 


87 


NS 


NS 


NS 


9,800 SE . 


585 


90 


NS 


NS 


NS 


9,800 SE 


643 


71 


NS 


NS 


NS 


9,825 SE . 


593 


98 


NS 


NS 


NS 


9,825 SE 


764 


60 


NS 


NS 


NS 


9,850 SE . 


591 


174 


NS 


NS 


NS 


9,850 SE 


701 


57 


NS 


NS 


NS 


9,875 SE 


631 


208 


NS 


NS 


NS 


9,875 SE 


655 


NR 


NS 


NS 


NS 


9.900 SE 


591 


196 


NS 


NS 


NS 


9,900 SE 


591 


66 


NS 


NS 


NS 


9,925 SE 


601 


188 


NS 


NS 


NS 


9,925 SE 


594 


63 


NS 


NS 


NS 


9,950 SE 


545 


165 


NS 


NS 


NS 


9,950 SE 


567 


61 


NS 


NS 


NS 


9,975 SE . 


527 


139 


NS 


NS 


NS 


9,975 SE 


568 


62 


NS 


NS 


NS 


10,000 SE 


521 


100 NS 
LINE 10,600 NE 


NS 


NS 


10,000 SE 


544 


62 


NS 


NS 


NS 








LINE 10,900 NE 






9,500 SE 


541 


86 


<50 


0.18 


200 


9,500 SE 


555 


83 


<50 


0.26 


210 


9,525 SE 


547 


101 


<50 


17 


200 


9,525 SE 


559 


90 


<50 


.13 


190 


9,550 SE 


553 


102 


<50 


.22 


200 


9,550 SE 


577 


88 


<50 


.13 


200 


9,575 SE 


592 


90 


<50 


.21 


220 


9,575 SE 


651 


84 


<50 


.14 


200 


9,600 SE 


715 


92 


<50 


16 


190 


9,600 SE 


735 


85 


<50 


.13 


190 


9,625 SE 


954 


99 


<50 


.28 


210 


9,625 SE 


909 


79 


<50 


.25 


200 


9,650 SE 


1159 


127 


<50 


5.10 


480 


9,650 SE 


962 


84 


<50 


.15 


180 


9,675 SE . 


722 


142 


480 


1.85 


290 


9,675 SE 


589 


84 


<50 


.17 


180 


9,700 SE 


593 


98 


270 


.26 


220 


9,700 SE , 


572 


89 


<50 


.15 


180 


9,725 SE . 


540 


97 


<50 


.17 


200 


9,725 SE 


581 


87 


<50 


.10 


180 


9,750 SE 


555 


99 


<.50 


.22 


230 


9,750 SE 


557 


114 


<50 


.23 


220 


9,775 SE . 


568 


98 


<50 


.20 


170 


9,775 SE 


574 


117 


<50 


.39 


390 


9,800 SE . 


586 


87 


<50 


.22 


190 


9,800 SE 


587 


90 


<50 


.20 


210 


9,825 SE . 


612 


83 


<50 


.16 


160 


9,825 SE 


608 


81 . 


<50 


.14 


160 


9,850 SE . 


671 


95 


<50 


.26 


250 


9,850 SE , 


607 


79 


<50 


.19 


180 


9.875 SE . 


558 


86 


<50 


.25 


250 


9,875 SE 


588 


72 


<50 


.13 


180 


9,900 SE . 


560 


77 


<50 


.36 


170 


9,900 SE 


736 


82 


<50 


.25 


280 


9,925 SE . 


556 


81 


<50 


.21 


180 


9,925 SE 


724 


86 


340 


2.43 


390 


9,950 SE . 


553 


76 


<50 


.25 


200 


9,950 SE 


566 


140 


<50 


1.05 


220 


9,975 SE . 


543 


83 


<50 


.24 


230 


9,975 SE 


546 


91 


100 


21 


260 


10,000 SE 


563 


83 


<50 




18 


190 


10,000 SE 


549 


85 


<50 


.38 


230 



NS No sample, NR No reading 

'Total-field magnetic intensity, all readings have a base of 56,000 gammas. 

^otal-count gamma-ray radiation 

^Soil sample analyses by XRF by Bureau's Reno Research Center, Reno, NV. 



RESULTS OF MAGNETIC,' RADIOMETRIC,^ AND SOIL SAMPLE^ SURVEYS— Continued 



29 



Station 


Magnetic 
intensity, 
gammas 


Radioactivity. 


Cb. 


P2O.. 


Zn. 


Station 


Magnetic 
intensity. 


Radioactivity, 


Cb. 


P205, 


Zn, 




cps 


ppm 


pet 


ppm 




gammas 


cps 


ppm 


pet 


ppm 






LINE 11.000 NE 










LINE 11,300 NE 






9.500 SE . 


558 


82 


NS 


NS 


NS 


9.500 SE 


523 


70 


<50 


0,17 


200 


9.525 SE . . 


554 


82 


NS 


NS 


NS 


9.525 SE 


524 


66 


<-50 


.16 


190 


9.550 SE . . 


577 


89 


NS 


NS 


NS 


9.550 SE 


516 


75 


<50 


.15 


190 


9.575 SE . 


575 


93 


NS 


NS 


NS 


9.575 SE 


521 


70 


<50 


.19 


190 


9.600 SE 


646 


86 


NS 


NS 


NS 


9.600 SE 


525 


69 


<50 


.16 


200 


9.625 SE 


700 


97 


NS 


NS 


NS 


9.625 SE 


528 


70 


<50 


.15 


200 


9.650 SE 


802 


95 


NS 


NS 


NS 


9.650 SE 


540 


68 


<50 


.21 


220 


9.675 SE . . 


614 


87 


NS 


NS 


NS 


9.675 SE . 


536 


65 


<50 


.14 


220 


9,700 SE . 


571 


79 


NS 


NS 


NS 


9.700 SE 


540 


71 


<50 


.13 


180 


9.725 SE . 


556 


80 


NS 


NS 


NS 


9.725 SE 


551 


77 


<50 


.14 


180 


9.750 SE 


545 


76 


NS 


NS 


NS 


9.750 SE 


519 


65 


<50 


.15 


210 


9.775 SE 


563 


76 


NS 


NS 


NS 


9.775 SE 


528 


77 


<50 


.12 


190 


9.800 SE 


569 


79 


NS 


NS 


NS 


9.800 SE 


530 


76 


<50 


.13 


200 


9.825 SE , 


577 


74 


NS 


NS 


NS 


9.825 SE 


526 


76 


<50 


.15 


200 


9.850 SE . 


592 


80 


NS 


NS 


NS 


9.850 SE . 


535 


83 


-.50 


.11 


190 


9.875 SE . 


623 


81 


NS 


NS 


NS 


9.875 SE 


540 


87 


<50 


.20 


200 


9.900 SE . 


687 


82 


NS 


NS 


NS 


9.900 SE 


535 


81 


<50 


.14 


200 


9.925 SE 


775 


83 


NS 


NS 


NS 


9.925 SE 


527 


66 


<50 


.14 


190 


9.950 SE 


784 


79 


NS 


NS 


NS 


9.950 SE 


525 


75 


<50 


.16 


180 


9.975 SE . , 


802 


79 


NS 


NS 


NS 


9.975 SE 


516 


82 


<50 


.17 


200 


10.000 SE 


549 


78 


NS 


NS 


NS 


10.000 SE 


549 


81 


<50 


.16 


200 


10.025 SE 


544 


75 


NS 


NS 


NS 


10.025 SE 


531 


73 


-50 


-18 


190 


















LINE 11.100 Nb 






10.050 SE 
10.075 SE 


532 
538 


74 
76 


<50 
<50 


.16 
.16 


190 


9.500 SE . , 


523 


83 


<50 


0.17 


200 


190 


9.525 SE , 


507 


93 


<50 


,20 


200 


10.100 SE 


528 


88 


<50 


.17 


190 


9.550 SE , 


506 


85 


<50 


,14 


200 


10,125 SE 


527 


81 


<50 


.20 


190 


9,575 SE 


520 


90 


<50 


.15 


180 


10,150 SE 


556 


85 


<50 


.13 


190 


9,600 SE , 


536 


85 


<50 


.10 


190 


10.175 SE 


565 


76 


<50 


-15 


200 


9.625 SE 


562 


87 


<50 


.19 


240 


10.200 SE 


545 


76 


-50 


-14 


180 


9,650 SE . 


562 
624 


84 

85 


<50 

<50 


.15 
.12 


190 

180 






LINE 11.500 NE 






9,675 SE 


9.500 SE 


540 


69 


NS 


NS 


NS 


9,700 SE . . 


771 


82 


<50 


.11 


190 


9.525 SE 


528 


69 


NS 


NS 


NS 


9.725 SE . . 


946 


86 


<50 


.15 


190 


9.550 SE 


533 


69 


NS 


NS 


NS 


9.750 SE 


660 


85 


<50 


.18 


190 


9.575 SE 


528 


77 


NS 


NS 


NS 


9.775 SE . , 


585 


78 


<50 


.15 


200 


9.600 SE . 


519 


77 


NS 


NS 


NS 


9.800 SE . 


566 


82 


<50 


.14 


210 


9.625 SE 


520 


82 


NS 


NS 


NS 


9.825 SE 


580 


86 


<50 


.10 


200 


9.650 SE 


519 


84 


NS 


NS 


NS 


9.850 SE . , 


573 


87 


<50 


.12 


200 


9.675 SE 


522 


81 


NS 


NS 


NS 


9.875 SE , , 


580 


82 


<50 


.17 


210 


9.700 SE 


530 


82 


NS 


NS 


NS 


9.900 SE . . 


611 


88 


<50 


-15 


200 


9.725 SE 


541 


74 


NS 


NS 


NS 


9.925 SE , 


594 


86 


<50 


.20 


200 


9.750 SE 


533 


79 


NS 


NS 


NS 


9.950 SE . 


613 


84 


<50 


.14 


190 


9.775 SE 


537 


85 


NS 


NS 


NS 


9.975 SE . . 


599 


82 


<50 


.17 


190 


9.800 SE 


532 


85 


NS 


NS 


NS 


10,000 SE 


600 


75 


<50 


.21 


190 


9.825 SE . 


530 


84 


NS 


NS 


NS 


10,025 SE 


595 


NR 


<50 


.18 


180 


9.850 SE . 


514 


85 


NS 


NS 


NS 


10,050 SE 


551 


NR 


NS 


NS 


NS 


9.875 SE . 


511 


80 


NS 


NS 


NS 


10.075 SE 


530 


NR 


NS 


NS 


NS 


9.900 SE . 


512 


82 


NS 


NS 


NS 


10.100 SE 


539 


NR 


NS 


NS 


NS 


9.925 SE 
9.950 SE 


502 
506 


77 
77 


NS 
NS 


NS 
NS 


NS 
NS 


















LINE 11,200 Nt 






9.975 SE 
10.000 SE 


510 
511 


76 
75 


NS 
NS 


NS 
NS 


NS 


9,500 SE . . 


547 


84 


NS 


NS 


NS 


NS 


9,525 SE . . 


550 


81 


NS 


NS 


NS 














9,550 SE . . 


536 


90 


NS 


NS 


NS 


10.025 SE 


533 


81 


NS 


NS 


NS 


9,575 SE .. 


530 


88 


NS 


NS 


NS 


10.050 SE 


527 


81 


NS 


NS 


NS 


9,600 SE . . 


543 


• 92 


NS 


NS 


NS 


10.075 SE 


521 


79 


NS 


NS 


NS 


9,625 SE 


557 


85 


NS 


NS 


NS 


10.100 SE 


521 


81 


NS 


NS 


NS 


9,650 SE . 


600 


82 


NS 


NS 


NS 


10,125 SE 


514 


87 


NS 


NS 


NS 














10.150 SE 


531 


88 


NS 


NS 


NS 


9,675 SE .. 


650 


80 


NS 


NS 


NS 


10.175 SE 


535 


80 


NS 


NS 


NS 


9.700 SE . . 


808 


82 


NS 


NS 


NS 














9,725 SE . . 


625 


87 


NS 


NS 


NS 


10.200 SE 


532 


81 


NS 


NS 


NS 


9.750 SE . 


498 


92 


NS 


NS 


NS 


10.225 SE 


532 


85 


NS 


NS 


NS 


9.775 SE , . 


506 


77 


NS 


NS 


NS 


10.250 SE 


539 


81 


NS 


NS 


NS 


9,800 SE . 


508 


78 


NS 


NS 


NS 


10.275 SE 


531 


79 


NS 


NS 


NS 


9,825 SE . . 


515 


70 


NS 


NS 


NS 


10.300 SE 


535 


78 


NS 


NS 


NS 














10.325 SE 


531 


82 


NS 


NS 


NS 


9.850 SE . . 


529 


79 


NS 


NS 


NS 


10,350 SE 


530 


64 


NS 


NS 


NS 


9.875 SE . . 


528 


82 


NS 


NS 


NS 














9.900 SE . . 


543 


82 


NS 


NS 


NS 


10.375 SE 


531 


69 


NS 


NS 


NS 


9.925 SE . . 


540 


88 


NS 


NS 


NS 


10.400 SE 


535 


72 


NS 


NS 


NS 


9.950 SE . . 


544 


87 


NS 


NS 


NS 














9.975 SE . . 


522 


82 


NS 


NS 


NS 


NS No ; 


sample. 


NR No reading. 








10.000 SE 


518 


76 


NS 


NS 


NS 


'Total-fiel 


d magnetic 


intensity, all readi 


ngs have 


a base of 56.000 gammas 














^otal-coL 


jnt gamma- 


ray radiation. 








10.025 SE 


527 


78 


NS 


NS 


NS 


^Soll sam 


pie analyses by XRF by Bureau s Reno Research Center, Reno, 


10,050 SE 


527 


77 


NS 


NS 


NS 














10,075 SE 


527 


78 


NS 


NS 


NS 














10,100 SE 


526 


75 


NS 


NS 


NS 














10.125 SE 
10,150 SE 


519 
522 


77 
80 


NS 
NS 


NS 
NS 


NS 
NS 










848^/ 


IGO 


10,175 SE 


522 


75 


NS 


NS 


NS 














10.200 SE 


521 


81 


NS 


NS 


NS 




























^U.S. Government Printir 


a Office 


: 1986 -168 


-198/50998 



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